Biological diversity as the most important factor in sustainable development. What threatens the decline in biodiversity

Abstract: Biodiversity

1. Introduction

2) Types of diversity

Species diversity

Genetic diversity

· Diversity of communities and ecosystems

3) Key species and resources

4) Measuring biodiversity

5) Optimal and critical levels of diversity

6) What kind of biodiversity is there?

7) Types of extinction

8) Goals of biodiversity management at the present stage

9) Ethical arguments for biodiversity conservation

10) Conclusion

11) List of references used

MINISTRY OF EDUCATION OF THE RUSSIAN FEDERATION

ROSTOV STATE UNIVERSITY

PSYCHOLOGY FACULTY

ABSTRACT

at the rate:

"Concepts of Modern Natural Science"

"The role of biodiversity in wildlife"

Performed:

4th year student, 1st group

day department

Faculty of Psychology

Bronevich Marina

Rostov-on-Don

According to the definition given by the World Wildlife Fund (1989), biological

diversity is “the entire diversity of life forms on earth, millions of species

plants, animals, microorganisms with their sets of genes and complex ecosystems,

forming wildlife" Thus, biological diversity should

considered at three levels. Biological diversity at the species level

covers the entire range of species on Earth from bacteria and protozoa to the kingdom

multicellular plants, animals and fungi. On a smaller scale

biological diversity includes the genetic diversity of species,

formed both by geographically distant populations and by individuals within

the same population. Biological diversity also includes

diversity of biological communities, species, ecosystems formed

communities and interactions between these levels (Fig. 1).

Rice. 1 Biological diversity includes genetic diversity

(hereditary variability within each species), species diversity(kit

species in a given ecosystem) and diversity of communities/ecosystems (habitats and

ecosystems in a given area)

All levels are necessary for the continued survival of species and natural communities.

biological diversity, all of which are important for humans. Variety of species

demonstrates the richness of evolutionary and ecological adaptations of species to

various environments. Species diversity serves as a source for humans

variety of natural resources. For example, tropical rainforests with their

rich variety of species produce a remarkable diversity of plant and

animal products that can be used for food, construction and

medicine. Genetic diversity is necessary for any species to survive

reproductive viability, disease resistance, ability to

adaptation in changing conditions. Genetic diversity of domestic animals

animals and cultivated plants are especially valuable for those who work on

breeding programs to maintain and improve modern

agricultural species.

Community-level diversity represents the collective response of species

to various environmental conditions. Biological communities characteristic

for deserts, steppes, forests and flooded lands, maintain continuity

normal functioning of the ecosystem, providing its “service”,

for example, through flood control, protection against soil erosion,

air and water filtration.

2. Species diversity

At each level of biological diversity - species, genetic and

diversity of communities, experts study the mechanisms that change or

maintain diversity. Species diversity includes the entire range of species

living on Earth. There are two main definitions of the concept of species. First:

a species is a collection of individuals that, for one reason or another,

differs in morphological, physiological or biochemical characteristics

from other groups. This is the morphological definition of the species. Now to differentiate

species that are almost identical in appearance (for example, bacteria) are increasingly

use differences in DNA sequence and other molecular markers.

The second definition of a species is a collection of individuals between which there is

free crossing, but there is no crossing with individuals of other

groups (biological definition of species).

3. Genetic diversity

Genetic diversity within species is often provided by reproductive

behavior of individuals within a population. A population is a group of individuals of the same

species that exchange genetic information among themselves and produce fertile

offspring. A species may contain one or more distinct populations. Population

can consist of several individuals or millions.

Individuals within a population are usually genetically different from each other.

Genetic diversity is due to the fact that individuals have slightly

differing genes - sections of chromosomes that encode certain

proteins. Variants of a gene are known as its alleles. Differences arise from mutations

– changes in the DNA that is found in the chromosomes of a particular individual. Alleles

genes can have different effects on the development and physiology of an individual. Breeders

varieties of plants and animal breeds, selecting certain gene variants,

create high-yielding, pest-resistant species, such as cereals

crops (wheat, corn), livestock and poultry.

4. Diversity of communities and ecosystems

A biological community is defined as a collection of individuals of different

species living in a certain territory and interacting with each other.

Examples of communities are coniferous forests, tallgrass prairies, tropical rainforests

forests, coral reefs, deserts. The biological community together with

its habitat is called an ecosystem. In terrestrial ecosystems, water

evaporated by biological objects from the surface of the Earth and from water

surfaces to fall again as rain or snow and replenish

terrestrial and aquatic environments. Photosynthetic organisms absorb light energy

which is used by plants for their growth. This energy is absorbed

animals that eat photosynthetic organisms or is released as

heat both during the life of organisms and after their death and

decomposition.

During photosynthesis, plant organisms absorb carbon dioxide and

produce oxygen, and animals and fungi absorb oxygen during respiration and

release carbon dioxide. Mineral nutrients such as nitrogen and

phosphorus, circulate between living and nonliving components of the ecosystem.

Physical properties of the environment, especially the annual temperature regime and

precipitation, affect the structure and characteristics of the biological community and

determine the formation of either a forest, or a meadow, or a desert or swamp.

The biological community, in turn, can also change physical

characteristics of the environment. In terrestrial ecosystems, for example, wind speed,

humidity, temperature and soil characteristics can be determined

influence of the plants and animals living there. In aquatic ecosystems such

physical characteristics such as turbulence and transparency of water, its

chemical characteristics and depth determine qualitative and quantitative

composition of aquatic communities; and communities such as coral reefs are themselves

significantly influence the physical properties of the environment. Inside

biological community, each species uses a unique set of resources,

which constitutes his niche. Any niche component can become limiting

factor when it limits population size. For example, populations of species

bats with highly specialized requirements for environmental conditions,

forming colonies only in calcareous caves, may be limited

number of caves with suitable conditions.

The composition of communities is largely determined by competition and predators. Predators

often significantly reduce the number of species - their prey - and may even

displace some of them from their usual habitats. When predators

are exterminated, the population size of their victims may increase to critical

level or even go beyond it. Then after exhaustion of the limiting resource

population destruction may begin.

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Introduction

The diversity of life has long been a subject of study. The first systems of living nature, known, for example, from the works of Aristotle (384-322 BC), already relate to the analysis of this phenomenon. The scientific and methodological basis for describing biodiversity was created by K. Liney in his “System of Nature”. And in the future there was an accumulation of knowledge.

And in the last decade, the term “biodiversity” has become extremely popular. Since the signing of the Convention on Biological Diversity by many states in 1992, this word has constantly been heard in government decrees, documents of state and public organizations, in media mass media. Scientific research has proven that a necessary condition for the normal functioning of ecosystems and the biosphere as a whole is a sufficient level of natural diversity on our planet. Currently, biological diversity is considered as the main parameter characterizing the state of supraorganismal systems. In a number of countries, it is the characteristics of biological diversity that serve as the basis for the environmental policy of the state, seeking to preserve its biological resources in order to ensure sustainable economic development.

Biodiversity conservation is discussed at the global, national, and regional levels. However, the meaning of this word is not understood correctly by everyone. Why is biodiversity given such attention, what role does it play in the lives of people and the planet, how is it changing, what threatens it and what needs to be done to preserve it - my work is devoted to answering these questions.

The purpose of the work was to study methods and assessments of biodiversity

During the work, the following tasks were set:

1) consider the concept of “biodiversity”;

2) identify features of biodiversity;

3) study methods and assessments of biodiversity.

The object of the study was biological diversity as the diversity of natural ecosystems on the globe.

The subject of study was current state biological diversity.

biological environmental policy

Biological diversity

Biodiversity concept

The phrase “biological diversity”, as noted by N.V. Lebedev and D.A. Krivolutsky, was first used by G. Bates in 1892 in the famous work “A Naturalist in the Amazon,” when he described his impressions of meeting seven hundred species of butterflies during an hour-long excursion. The term “biodiversity” came into wide scientific use in 1972 after the Stockholm UN Conference on the Environment, when ecologists managed to convince political leaders countries of the world community is that wildlife protection is a priority task for any country.

Biological diversity is the totality of all biological species and biotic communities formed and emerging in different habitats (terrestrial, soil, marine, freshwater). This is the basis for maintaining the life-supporting functions of the biosphere and human existence. National and global problems of biodiversity conservation cannot be realized without basic research in this area. Russia, with its vast territory, which preserves the main diversity of ecosystems and species diversity of Northern Eurasia, needs the development of special research aimed at inventorying, assessing the state of biodiversity, developing a system for its monitoring, as well as developing principles and methods for the conservation of natural biosystems.

According to the definition given by the World Wildlife Fund, biodiversity is “the entire diversity of life forms on earth, the millions of species of plants, animals, microorganisms with their sets of genes and the complex ecosystems that make up living nature.” With such a broad understanding of biodiversity, it is advisable to structure it in accordance with the levels of organization of living matter: population, species, community (a set of organisms of one taxonomic group in homogeneous conditions), biocenosis (a set of communities; biocenosis and environmental conditions are an ecosystem), territorial units of a larger rank - landscape, region, biosphere.

The biological diversity of the biosphere includes the diversity of all species of living beings inhabiting the biosphere, the diversity of genes that form the gene pool of any population of each species, as well as the diversity of biosphere ecosystems in different natural areas. The amazing diversity of life on Earth is not just the result of the adaptation of each species to specific environmental conditions, but also the most important mechanism for ensuring the sustainability of the biosphere. Only a few species in an ecosystem have significant numbers, biomass and productivity. Such species are called dominant. Rare or scarce species have low numbers and biomass. As a rule, dominant species are responsible for the main flow of energy and are the main environment-formers, strongly influencing the living conditions of other species. Small species form a kind of reserve even when various external conditions they can become part of the dominant species or take their place. Rare species mainly create species diversity. When characterizing diversity, indicators such as species richness and evenness of distribution of individuals are taken into account. Species richness is expressed as the ratio of the total number of species to the total number of individuals or per unit area. For example, in two communities with equal conditions inhabited by 100 individuals. But in the first, these 100 individuals are distributed among ten species, and in the second, among three species. In the example given, the first community has richer species diversity than the second. Let us assume that in both the first and second communities there are 100 individuals and 10 species. But in the first community, individuals are distributed between species, 10 each, and in the second, one species has 82 individuals, and the rest have 2. As in the first example, the first community will have a greater evenness in the distribution of individuals than the second.

The total number of currently known species is about 2.5 million, and almost 1.5 million of them are insects, another 300 thousand are flowering plants. There are about as many other animals as there are flowering plants. There are a little more than 30 thousand known algae, about 70 thousand fungi, less than 6 thousand bacteria, and about a thousand viruses. Mammals - no more than 4 thousand, fish - 40 thousand, birds - 8400, amphibians - 4000, reptiles - 8000, mollusks - 130,000, protozoa - 36,000, various worms - 35,000 species.

About 80% of biodiversity consists of land species (terrestrial, air and soil habitats) and only 20% - species aquatic environment life, which is quite understandable: the diversity of environmental conditions in water bodies is lower than on land. 74% of biodiversity is due to tropical zone. 24% - from temperate latitudes and only 2% - from polar regions.

Since tropical forests are disappearing catastrophically quickly under the pressure of plantations of hevea, bananas and other highly profitable tropical crops, as well as sources valuable wood, much of the biological diversity of these ecosystems may die without ever receiving scientific names. This is a depressing prospect, and so far the efforts of the global environmental community have not yielded any tangible results in preserving tropical forests. The lack of complete collections also makes it impossible to reliably judge the number of species living in marine environments, which have become “... a kind of limit to our knowledge of biological diversity.” IN last years It is in marine environments that completely new groups of animals are discovered.

To date, the planet's biodiversity has not been fully identified. According to forecasts, the total number of species of organisms living on Earth is at least 5 million (and according to some forecasts - 15, 30 and even 150 million). The least studied are the following systematic groups: viruses, bacteria, nematodes, crustaceans, unicellular organisms, algae. Mollusks, mushrooms, arachnids and insects have also been insufficiently studied. Only vascular plants, mammals, birds, fish, reptiles, and amphibians have been well studied.

Microbiologists have learned to identify fewer than 4,000 species of bacteria, but research on bacterial DNA analysis carried out in Norway has shown that more than 4,000 species of bacteria live in 1 g of soil. A similarly high bacterial diversity is predicted in marine sediment samples. The number of bacterial species that have not been described is in the millions.

The number of species of living organisms living in marine environments has not been fully identified. “The marine environment has become the frontier of our knowledge of biological diversity.” New groups of marine animals of high taxonomic rank are constantly being identified. Communities of organisms unknown to science have been identified in recent years in the canopy of tropical forests (insects), in geothermal oases depths of the sea(bacteria and animals), in the depths of the earth (bacteria at a depth of about 3 km).

The number of described species is indicated by the shaded parts of the bars.

Diversity of species in nature, its reasons. The influence of human activities on species diversity. Biological progress and regression

Biological diversity

Biodiversity is a concept that refers to all the diversity of life on Earth and all existing natural systems. The biodiversity we see today is the product of evolution over billions of years, determined by natural processes and increasingly by human influence. It represents the fabric of Life, integral part which we are and on which we are completely dependent.

They say that there are many more species of life on Earth than there are stars in the sky. To date, about 1.7 million species of plants, animals and microorganisms have been identified and given their names. We are also one of these species. The exact number of species living on Earth is still not known. Their number ranges from 5 to 100 million!

Biological diversity is an invaluable global asset for present and future generations. But today the number of threats to the gene pool, species and ecosystems is greater than ever before. As a result of human activity, ecosystems are degraded, species die off or their numbers decline at alarming rates to unsustainable levels. This loss of biodiversity undermines the very basis of Life on Earth and is truly a global tragedy.

According to various sources, from 100 to 200 species become extinct every 24 hours! They disappear forever! Their disappearance in most cases goes unnoticed, since only a small part of them is identified. Living species have been disappearing at a rate 50 to 100 times the natural rate, and the rate is expected to increase significantly. According to estimates based on current trends, 34 thousand plant species and 5.2 thousand animal species (including an eighth! part of bird species) are threatened with complete extinction. Humanity will certainly suffer (and is already suffering) from such losses, and not only because the world will be poorer without polar bears, tigers and rhinoceroses. The depletion of the world's biological heritage will limit the emergence of new healthy products. Only a small proportion of plant and animal species have been studied for their social utility. Only 5,000 of approximately 265,000 plant species are cultivated for food. Even the smallest species can play decisive role in the ecosystems to which they belong. People simply have no idea what they are neglecting. Natural wealth earth is not only a diversity of species, but also genetic codes that provide each Living being characteristics that allow it to survive and develop. These genes can be used to develop drugs and expand the range of food products. More than half of all are obtained from plants medicines. According to UNEP, more than 60% of people in the world directly depend on plants from which they obtain medicines. In China, for example, more than 5,000 of the 30,000 identified domestic plant species are used for medicinal purposes. More than 40% of prescriptions written in the United States contain one or more drugs derived from wild species(fungi, bacteria, plants and animals). In addition to their medicinal value, wild plant and animal species also have other high commercial values. They are very important for industry as sources of tannin, rubber, resin, oils and other commercially valuable components. The potential for new industrial products from unknown or poorly known plant and animal species is enormous. Such products may even contain hydrocarbons that could replace oil as an energy source. For example, a tree that grows only in northern Brazil produces about 20 liters of sap every 6 months. This juice can be used as fuel for engines. Brazil also produces methane from grains, which they then sell for use in cars. The production and use of methane saves the country $6 million in foreign currency every year. Biodiversity loss reduces the productivity of ecosystems, thereby reducing the natural basket of goods and services from which we continually draw. It destabilizes ecosystems and reduces their ability to withstand various natural disasters. We spend huge amounts of money to repair damage from hurricanes and floods, an increasing number of which are a consequence of deforestation and global warming. By losing diversity, we lose cultural identity, which is rooted in the biological environment around us. Plants and animals are our symbols, their images appear on flags, in sculptures and other images of us and our society. We draw inspiration from admiring the beauty and power of nature. The loss of biodiversity is irreversible under current conditions, and given our dependence on crop yields, medicines and other biological resources, it poses a threat to our well-being.

Causes of biodiversity loss

The predominant causes of loss of biodiversity and degradation of biological resources (and simply LIFE on Earth) are large-scale deforestation and burning, destruction of coral reefs, uncontrolled fishing, excessive destruction of plants and animals, illegal trade in species wild fauna and flora, use of pesticides, drainage of swamps, air pollution, use of corners untouched nature for agricultural needs and urban construction.

Forests inhabit most of the known terrestrial species, however, 45% of the Earth's natural forests have disappeared, mostly cut down, over the last century. Despite all efforts, the world's forest area is rapidly declining. Up to 10% of coral reefs - one of the richest ecosystems - have been destroyed, and 1/3 of the remaining will die in the next 10-20 years! Coastal mangroves - vital habitat The habitat for the young of many animal species is also under threat, and half of them have already disappeared. Depletion of the ozone layer causes more ultraviolet rays to reach the Earth's surface, where they destroy living tissue. Global warming is changing the habitats and distribution of species. Many of them will die if the average annual temperature on Earth increases.

How the Convention came about

Back in November 1988, the United Nations Environment Program (UNEP) organized an Ad Hoc Working Group of Experts on biological diversity to explore the need to develop an international convention on biological diversity. In May 1989, it established an Ad Hoc Working Group on Technical and Legal Issues to prepare an international legal instrument regarding the conservation and sustainable use of biological diversity.

Since February 1991 Special working group became known as the Intergovernmental Negotiating Committee. The result of the committee's work was the holding of the Conference on the Harmonization of the Text of the Convention on Biological Diversity on May 22, 1992 in Nairobi, Kenya. The Convention on Biological Diversity was signed on June 5 by the leaders of 150 countries at the historic Earth Summit in Rio de Janeiro in 1992.

Which spread and live in various natural areas. Such biodiversity is not the same in different climatic conditions: some species adapt to harsh conditions Arctic and tundra, others learn to survive in deserts and semi-deserts, others love the warmth of tropical latitudes, others inhabit forests, and others spread across the wide expanses of the steppe. The state of species that currently exists on Earth was formed over 4 billion years. However, one of them is the reduction of biodiversity. If it is not solved, then we will forever lose the world we know now.

Reasons for the decline in biodiversity

There are many reasons for the decline of animal and plant species, and all of them directly or indirectly come from people:

• expansion of the territories of settlements;
• regular emissions of harmful elements into the atmosphere;
• transformation of natural landscapes into agricultural sites;
• usage chemical substances in agriculture;
• pollution of water bodies and soil;
• construction of roads and position of communications;
• , requiring more food and territory for life;
• experiments on crossing plant and animal species;
• destruction of ecosystems;
• caused by people.

Of course, the list of reasons goes on. Whatever people do, they influence the reduction of habitats of flora and fauna. Accordingly, the life of animals changes, and some individuals, unable to survive, die prematurely, and the population size is significantly reduced, often leading to the complete extinction of the species. Approximately the same thing happens with plants.

The value of biodiversity

Biological diversity different forms life - animals, plants and microorganisms is valuable in that it has genetic and economic, scientific and cultural, social and recreational, and most importantly - ecological significance. After all, the diversity of animals and plants makes up the natural world all around us, so it needs to be protected. People have already caused irreparable damage that cannot be repaired. For example, many species across the planet were destroyed:

Quagga

Silphium

Solving the problem of biodiversity conservation

In order to preserve biodiversity on earth, a lot of effort needs to be made. First of all, it is necessary that the governments of all countries pay attention to Special attention this problem and defended natural objects from the attacks of different people. Also, work to preserve the world of flora and fauna is carried out by various international organizations, in particular Greenpeace and the UN.

Among the main measures that are being taken, it should be mentioned that zoologists and other specialists are fighting for every individual of an endangered species, creating nature reserves and natural parks where animals are monitored, creating conditions for them to live and increase populations. Plants are also artificially bred to expand their habitats and prevent valuable species from dying.
In addition, it is necessary to take measures to preserve forests, protect water bodies, soil and atmosphere from pollution, use them in production and everyday life. Most of all, the conservation of nature on the planet depends on ourselves, that is, on each person, because only we make the choice: kill an animal or save its life, cut down a tree or not, pick a flower or plant a new one. If each of us protects nature, the problem of biodiversity will be overcome.

LECTURE 3

TOPIC: Causes of biodiversity decline

PLAN:

1. Species extinction rates

2. Causes of species extinction

2.1. Habitat destruction

2.2. Habitat fragmentation

2.3. Edge effect

2.4. Habitat degradation and pollution

2.5. Overexploitation of resources

2.6. Invasive species

2.7. Diseases

3. Susceptibility to extinction

1. Species extinction rates

The most significant question for conservation biology is how long a given species can survive until complete disappearance, following extreme decline, degradation or fragmentation of its habitat? When the population size decreases to a certain critical level, the probability of its extinction becomes very high. In some populations, some remaining individuals may live for years or decades and even reproduce, but their future fate is still extinction, unless decisive measures are taken to preserve them. Particularly among woody vegetation, the last isolated non-reproductive specimens of a species may survive for hundreds of years. Such species are called potentially extinct: even if the species has not yet formally become extinct, the population is no longer able to reproduce, and the future of the species is limited by the lifespan of the remaining specimens. To successfully conserve species, scientists need to identify those human activities that affect the sustainability of populations and lead to species extinction. They must also identify factors that increase the susceptibility of populations to extinction.

The first noticeable impact of human activity on the rate of extinction was demonstrated by the destruction of large mammals in Australia, North and South America by people who inhabited these continents thousands of years ago. Soon after humans arrived, 74 to 86 percent of the megafauna—mammals weighing more than 44 kilograms—in these areas disappeared. This may have been directly related to hunting and indirectly to the burning and clearing of forests, as well as the spread of introduced diseases. Across all continents and numerous islands, there is a variety of striking evidence that the modification and destruction of habitats by prehistoric humans coincided with high rates of species extinction.

Currently, the extinction rates of birds and mammals are best studied because these relatively large animals are highly visible. The rate of extinction of the remaining 99.9% of the world's species remains quite approximate today. But the extent of the extinction of birds and mammals is determined very imprecisely, since some species that were considered extinct have been rediscovered, while others, on the contrary, were considered to still exist, may actually turn out to be extinct. The best estimate of available data is that about 85 species of mammals and 113 species of birds have disappeared since 1600, representing 2.1% of mammal species and 1.3% of birds that existed during this period. At first glance, these numbers in themselves do not seem alarming, but what has become alarming is the increasing rate of extinction over the past 150 years. During the period from 1600 to 1700, the rate of extinction of birds and mammals was approximately one species per decade, and during the period from 1850 to 1950 it increased to one species per year. This increase in the rate of species extinction indicates a serious threat to biological diversity.

At the same time, there is some evidence that the rate of extinction of birds and mammals has decreased in recent decades. This may be partly due to efforts being made to save species from extinction, but it is also an illusion created by the procedure adopted by international organizations whereby a species is considered extinct only if it has not been seen for more than 50 years or if Specially organized searches did not allow us to find a single remaining specimen. Many species, formally not yet completely extinct, have been greatly undermined by human activity and have survived only in very small numbers. These species may be considered ecologically extinct because they no longer play a role in community organization. The future of many of these species is uncertain.

About 11% of the world's remaining bird species are at risk of extinction; similar indicators were obtained for mammals and trees. The danger of extinction is equally great for some freshwater fish and shellfish. Plant species are also in a difficult situation. Gymnosperms (conifers, ginkgos, cycads) and palms are especially vulnerable. Although extinction is a natural process, more than 99% of extinctions modern species can be attributed to human activity.

2. Causes of species extinction

The main threats to biological diversity resulting from human activities are habitat destruction, fragmentation and degradation (including pollution), global climate change, human overexploitation of species, invasion of exotic species and the increasing spread of disease. Most species face at least two or more of these challenges, which are accelerating their extinction and hampering efforts to protect them.

All of these seven threats are caused by the increasing use of natural resources with an exponentially growing human population. Until the last few hundred years, population growth was relatively slow, with birth rates only slightly exceeding death rates. The greatest destruction of biological communities has occurred over the past 150 years, when the world's population grew from 1 billion people. in 1850 to 2 billion people. in 1930, and on October 12, 1998 amounted to 6 billion people.

2.1. Habitat destruction

The main threat to biological diversity is the destruction of habitats, and therefore the most important thing for the conservation of biological diversity is their protection. Loss of habitats involves both direct destruction and damage in the form of pollution and fragmentation. For most endangered plants and animals, habitat loss is the primary threat.

In many parts of the world, especially on islands and areas with high population densities, most primary habitats have already been destroyed. In Old World countries such as Kenya, Madagascar, India, the Philippines and Thailand, more than 50% of key forest habitats for biological diversity have been destroyed. Slightly better position in Democratic Republic Congo (formerly Zaire) and Zimbabwe; In these biologically rich countries, more than half of the habitats of wild species are still preserved. Many highly valuable wildlife species have lost much of their original range, and few of the remaining habitats are protected. For example, an orangutan ( Pongo pygmaeus), a large ape native to Sumatra and Borneo, has lost 63% of its habitat, and only 2% of its original range is protected.

The plight of tropical rainforests is perhaps the most widely known case of habitat destruction, but other habitats are also in mortal danger.

Biodiversity decline usually begins with the destruction of species' natural habitats. The development of new technologies and the destruction of the environment as a result of human activity is proceeding at a speed that significantly exceeds the ability of species to adapt to new conditions. The exception is a few species of animals and plants, which we call weeds and with which we do not want to share the future of the planet. It is likely that such insects and weeds have a range of hereditary variability that allows them to adapt to the rapid changes in the environment that occur as a result of its disturbance, but most larger plants and animals are unable to do this.

Human intervention often leads to a decrease in the diversity of natural conditions. For example, destroying different kinds tree species in mixed forests, in order to create preferable conditions for the growth of pine used in the pulp industry, humans inevitably reduce the number of ecological niches. As a result, in the resulting pure pine forests the species diversity of animals and plants decreases significantly compared to the original mixed forest community.

The destruction of a natural habitat often begins with its fragmentation into separate isolated areas. In the spring, wood grouse roosters gather to lek. The area of ​​forest required for current must be at least 5-8 hectares. The reduction of forest areas suitable for mating inevitably leads to a decline in the number of this species.

2.2. Habitat fragmentation

Habitat fragmentation is a process in which a continuous area of ​​habitat is simultaneously reduced and broken up into two or more fragments. Habitat destruction may not affect only local areas. These fragments are often separated from one another by altered or degraded landscape forms.

Fragments differ from the original continuous habitat in that: 1) the fragments have a relatively large extent border zones, adjacent to human activity and 2) the center of each fragment is located close to the edge. For example, consider a nature reserve square shape with a length of 1000 m (1 km) on each side, surrounded by human-used land such as farms. The total area of ​​such a reserve is 1 km2 (100 ha), its perimeter is 4000 m, and the point in the center of the reserve is 500 m from the nearest point of the perimeter. If domestic cats, in search of food, go deep into the forest 100 meters from the border of the reserve and prevent forest birds from raising their chicks, then only 64 hectares of the reserve remain suitable for the quiet breeding of birds. The peripheral strip unsuitable for reproduction occupies 36 hectares.

Now imagine a reserve divided into four equal parts by a road from north to south, 10 m wide, and a railway from east to west, also 10 m wide. The alienated area in the reserve as a whole is 2 hectares (2x1000x10 m). Since only 2% of the reserve's area is taken over by roads and railways, government officials say their impact on the reserve is negligible. But the reserve is now divided into 4 fragments, each with an area of ​​495 x 495 m, and the distance from the center of the fragment to the nearest perimeter point has been reduced to 240 m, that is, more than half. Since cats can now feed in the forest, entering it both from the perimeter and from the roads, the birds only have the internal areas of each of the four fragments for peaceful breeding. In a separate square, this area is 8.7 hectares, and in total they occupy 34.8 hectares in the reserve. Even if the highway Railway took away only 2% of the reserve's territory, they halved the habitats suitable for birds.

Habitat fragmentation threatens the existence of species in more complex ways. First of all, fragmentation limits the ability of species to disperse. Many species of birds, mammals and insects that live deep in the forest cannot cross even narrow strips of open space due to the danger of being caught by a predator. As a result, some species, after the disappearance of a population in a fragment, do not have the opportunity to repopulate it. Moreover, if the animals responsible for distributing the fleshy and sticky fruits disappear due to fragmentation, the corresponding plant species also suffer. Ultimately, isolated fragments of habitats are not populated by many of the species originally characteristic of them. And since within individual fragments there is a natural disappearance of species due to natural succession and population processes, and new species due to barriers cannot replenish their decline, therefore, a gradual depletion of species occurs in the fragment.

The second dangerous aspect of habitat fragmentation is that it reduces the foraging area for many typical animals. Many species of animals, represented by individuals or social groups that feed on widely scattered or seasonally available food and use seasonally distributed sources of water, require freedom of movement over a wide area. A life-saving resource may only be used for a few weeks a year or even once every few years, but when habitat is fragmented, isolated species are prevented from migrating within their native range in search of this rare but sometimes essential resource. For example, fences can impede the natural migration of large herbivores such as wildebeest or bison, forcing them to graze in one place, eventually leading the animals to starvation and habitat degradation.

Habitat fragmentation can also accelerate population decline by causing a widespread population to break up into two or more isolated subpopulations. These small populations are subject to their characteristic processes of inbreeding and genetic drift. If one integral large population can normally live in a large area of ​​habitat, then often none of its fragments can support a subpopulation large enough for long-term sustainable existence.

2.3. Edge effect

As shown above, habitat fragmentation greatly increases the proportion of edge habitats relative to interior habitats. These border, “edge” microenvironments differ from the inner forest part of the fragments. Edge habitats are characterized by large fluctuations in light levels, temperature, humidity and wind speed.

These edge effects spread deep into the forest up to 250 m. Since some species of animals and plants are very narrowly adapted to certain levels of temperature, humidity and light, they cannot withstand the changes that have arisen and disappear in forest fragments. Shade-tolerant species of wild flowering plants in forests temperate climate, late-successional tropical forest tree species and moisture-sensitive animals such as amphibians can become extinct very quickly due to habitat fragmentation, ultimately leading to shifts in species composition communities.

Due to forest fragmentation, wind exposure increases, humidity decreases and temperature rises and, as a result, the risk of fires increases. Fires can spread to forest fragments of habitats from surrounding agricultural lands, where, for example, sugar cane is burned or during slash-and-burn agriculture.

In Borneo and the Brazilian Amazon, millions of hectares of tropical rainforest burned during an unusually dry spell in 1997 and 1998. This environmental catastrophe was led to by a combination of factors caused by forest fragmentation as a result of agricultural activities and patchy settlements and the associated scattered accumulation of garbage and, accordingly, outbreaks of local fires.

Fragmentation of habitats makes, among other things, inevitable contact between wild animals and plants and domestic ones. As a result, diseases in domestic animals spread rapidly among wild species lacking adequate immunity. It should be borne in mind that such contact also ensures the transmission of diseases from wild species of plants and animals to domestic ones, and even to humans.

2.4. Habitat degradation and pollution

Environmental pollution is the most universal and severe form of its destruction. It is most often caused by pesticides, fertilizers and chemicals, industrial and municipal wastewater, gas emissions from factories and automobiles, and sediments washed in from upland areas. Visually, these types of pollution are often not very noticeable, although they occur around us every day in almost every part of the world. The global impact of pollution on water quality, air quality and even the planet's climate is in the spotlight, not only because of the threat to biodiversity, but also because of the impact on human health. Although environmental pollution is sometimes very visible and frightening, such as in the case of the massive oil spills and 500 oil well fires that occurred during the Gulf War, it is the hidden forms of pollution that are most dangerous, mainly because their effects does not appear immediately.

2.5. Overexploitation of resources

In order to survive, man has always hunted, collected fruits, used Natural resources. As long as the population was small and its technology primitive, man could sustainably exploit its environment, hunt and harvest without driving the desired species to extinction. However, as the population has increased, the pressure on the environment has increased. Crop farming methods have become incomparably more extensive and efficient, and have led to the almost complete displacement of large mammals from many biological communities, resulting in strangely “empty” habitats. In tropical forests and savannas, hunting rifles replaced bows, darts and arrows. In all the oceans of the world, powerful fishing motor vessels and fish processing “floating motherships” are used to catch fish. Small-scale fishing businesses are outfitting their boats and canoes with outboard motors, allowing them to harvest their catch faster and from a larger area than previously possible. Even in pre-industrial societies, overexploitation of resources led to the decline and extinction of native species. For example, the ceremonial cloaks of the Hawaiian kings were made from the feathers of one of the types of flower girls (Drepanis sp.). One cloak required feathers from 70 thousand birds of this now extinct species. Predatory species can reduce their numbers if their main prey is overharvested by humans. It is estimated that in the United States, overexploitation threatens the existence of about a quarter of endangered vertebrate species, and of these, about half are mammals.

IN traditional societies restrictions on the overexploitation of natural resources are often introduced: rights to use agricultural land are strictly controlled; hunting is prohibited in certain areas; there are prohibitions on the destruction of females, young animals and animals with low numbers; the collection of fruits is not permitted during certain seasons of the year and time of day, or barbaric methods of collection are prohibited. These types of restrictions allow traditional societies to use natural resources on a long-term sustainable basis, such as the strict fishing restrictions developed and proposed to the fisheries of many industrialized countries.

However, in many parts of the world, resources are now being exploited at their maximum intensity. If there is a demand for a product, the local population finds ways to find and sell it. Regardless of whether people are poor and hungry or rich and greedy, they use any available methods to obtain this product. Sometimes in traditional societies, decisions are made to sell ownership of a resource, such as a forest or a mine, in order to use the money to buy desired or needed goods. IN rural areas Traditional controls on the consumption of natural products may be weakened, and in many areas with significant population migration or where civil unrest and war occur, such controls do not exist at all. In countries involved in civil wars And internal conflicts, for example in Somalia, the former Yugoslavia, the Democratic Republic of the Congo and Rwanda, the population received firearms, and the food distribution system was destroyed. In such situations, natural resources are used by anyone who wishes it. At the local or regional level, in developing countries ah, hunters penetrate into newly inhabited territories, into national parks, and other places where roads pass, and hunt down any large animal here to sell the so-called “wild meat”. This leads to the formation of “forest wastelands” - lands with almost intact plant communities, but without characteristic animal communities. In order to satisfy legal and illegal demands, entire biological communities are destroyed. Collectors catch a huge number of butterflies and other insects, remove orchids, cacti and other plants from nature, sea ​​mollusks for the sake of shells and tropical fish for aquarists.

In many cases, the mechanism of overexploitation is notorious. A resource is identified, a market is identified for it, and then the local population is mobilized to extract and sell it. A resource is consumed so widely that it becomes rare or even disappears, and the market introduces another species, resource, or opens up a new region for exploitation. According to this scheme, industrial fishing is carried out, when one species after another is consistently produced until exhaustion. Loggers often do the same thing, gradually cutting down less and less in successive cycles. valuable trees until only a few commercial trees remain in the forest. Hunters, too, are gradually moving further and further from their villages and from the logger camps in search of animals and catch them for themselves or for sale.

For many exploited species, the only chance of recovery is when they become so rare that they are no longer commercially valuable. Unfortunately, the population size of many species, such as rhinoceroses and some wild cats, has already been so severely reduced that these animals are unlikely to be able to recover. In some cases, their rarity may even increase demand. As rhinos become increasingly rare, the price of rhino horn increases, making it a more valuable commodity on the black market. In rural areas of developing countries, desperate people are actively searching for the last remaining food to feed their families. rare plants or animals, so that after getting them, they can sell them and buy food for their family. In such situations, one of conservation biology's priorities is to find ways to protect and support the remaining members of these species.

2.6. Invasive species

The geographic ranges of many species are limited primarily by natural and climatic barriers. North American mammals are unable to cross the Pacific Ocean to Hawaii, fish Caribbean Sea cannot cross Central America and reach Pacific Ocean, A freshwater fish from one African lake There is no way they can cross the land and get into other neighboring isolated lakes. Oceans, deserts, mountains, rivers all limit the movement of species. Thanks to geographic isolation, the evolutionary paths of animals in each part of the world took their own path. By introducing alien species into these faunal and floristic complexes, man has disrupted the natural course of events. In pre-industrial eras, people, exploring new territories, brought cultivated plants and domestic animals with them. European sailors, in order to provide themselves with food on the way back, left goats and pigs on uninhabited islands. IN modern era, intentionally or accidentally, a huge number of species have been introduced into areas where they never existed. The introduction of many species was due to the following factors.

· European colonization. Arriving at new places of settlement in New Zealand, Australia, South Africa, and wanting to make the surroundings more familiar to the eye and provide themselves with traditional entertainment (in particular, hunting), Europeans brought there hundreds of European species of birds and mammals.

· Gardening and Agriculture. Large number of species ornamental plants, crops and pasture grasses are introduced and grown in new areas. Many of these species have “broken free” and established themselves in local communities.

The vast majority of exotic species, that is, species that find themselves outside their natural range due to human activity, do not take root in new places because the new environment does not meet their needs. However, a certain percentage of species become very well established in new “homes” and become invasive species, that is, those that increase in number at the expense of the original species. By competing for a limiting resource, such exotic species may displace native species. Introduced animals can exterminate the latter to the point of extinction, or they can change habitats so much that they become unsuitable for the original species. In the United States, invasive exotic species pose a threat to 49% of endangered species, with a particular threat to birds and plants.

Invasive species have had an impact in many areas globe. The United States is now home to more than 70 species of exotic fish, 80 species of exotic shellfish, 200 species of exotic plant species, and 2,000 exotic insects.

Many flooded lands in North America are absolutely dominated by exotic perennials: loosestrife is dominant in the marshes of eastern North America. Lythrum salicaria) from Europe, and Japanese honeysuckle ( Lonicera japonica) forms dense thickets in the lowlands of the southeastern United States. Intentionally introduced insects, such as European honey bees ( Apis mellifera) and bumblebees ( Bombus spp..), and accidentally introduced Richter ants ( Solenopsis saevissima richteri) and African honey bees (A. mellifera adansonii or A. mellifera scutella) created huge populations. These invasive species can have a devastating impact on the local insect fauna, leading to a decline in the numbers of many species in the area. In some areas of the southern United States, insect species diversity has decreased by 40% due to the infestation of exotic Richter's ants.

The impact of invasive species can be particularly severe in lakes, rivers and entire marine ecosystems. Freshwater communities are similar to ocean islands in that they are isolated habitats surrounded by vast, uninhabitable areas. They are therefore particularly vulnerable to the introduction of exotic species. Non-native species are often introduced into water bodies for commercial or sport fishing. More than 120 species of fish have already been introduced into marine and estuarine systems and inland seas; and although some of these introductions were carried out deliberately to improve fisheries, most of them were the unintended result of the construction of canals and the transfer of ballast water by ships. Exotic species are often larger and more aggressive than native fish species, and through competition and direct predation they can gradually drive native fish species to extinction.

Aggressive aquatic exotic fauna, along with fish, includes plants and invertebrates. In North America, one of the most alarming invasions was the appearance of the zebra mussel in the Great Lakes in 1988. Dreissena polymorpha). This small striped animal from the Caspian Sea was undoubtedly brought from Europe by tankers. Over two years, in some parts of Lake Erie, the number of zebra mussels reached 700 thousand individuals per 1 m2, which displaced local species of mollusks. As it moves south, this exotic species causes enormous economic damage to fisheries, dams, power plants and ships, and devastates aquatic communities.

2.7. Diseases

Second, an organism's susceptibility to disease may be an indirect result of habitat destruction. When habitat destruction causes a host population to become concentrated in a small area, this often leads to a deterioration in the quality of the environment and a decrease in the amount of food available, which leads to poor nutrition, weaker animals and, therefore, greater susceptibility to infection. Overpopulation can lead to social stress within the population, which also reduces the resistance of animals to diseases. Pollution increases the body's susceptibility to pathogenic infections, especially in aquatic environments.

Third, in many protected areas, zoos, national parks and new agricultural areas, wild animals come into contact with new species, including humans and domestic animals, with which they rarely or never encounter in the wild and therefore , exchange pathogens with them.

Some dangerous infectious diseases, such as human immunodeficiency virus (HIV) and Ebola virus, have likely spread from wild animal populations to domestic animals and humans. Once infected with exotic diseases, animals cannot be returned from captivity to wildlife without the threat of infecting the entire wild population. In addition, species that are resistant to a disease can become custodians of that pathogen, which can subsequently infect populations of less resistant species. For example, when kept together in zoos, completely healthy African elephants can transmit the herpes virus, which is deadly to them, to their relatives Asian elephants. In the early 90s in National Park In the Serengeti region of Tanzania, about 25% of lions died from canine distemper, apparently contracted through contact with one or more of the 30,000 domestic dogs living near the park. Diseases can also affect more common species: North American chestnut ( Castanea dentata), very widespread throughout the western United States, was virtually destroyed in this region by actinomycete fungi that came here with the Chinese chestnut introduced to New York. Currently, introduced fungi are destroying Florida dogwood ( Cornus florida) throughout much of its native range.

3. Susceptibility to extinction

When the environment is disrupted by human activity, the population size of many species declines and some species go extinct. Ecologists have observed that not all species have the same probability of extinction; certain categories of species are especially susceptible to it and require careful protection and control.

· Species with narrow ranges. Some species are found only in one or a few places geographically limited areas, and if the entire range is exposed to human activity, these species may become extinct. Numerous examples of this are the extinct species of birds that lived on oceanic islands. Many species of fish that lived in a single lake or river basin also disappeared.

· Species formed by one or more populations. Any population of species can become locally extinct as a result of earthquakes, fires, disease outbreaks and human activity. Therefore, species with many populations are less susceptible to global extinction than species that are represented by only one or a few populations.

· Species with small population size, or the “small population paradigm”. Small populations are more likely to go extinct than large ones because they are more susceptible to demographic and environmental changes and loss of genetic diversity. Species characterized by small population sizes, e.g. large predators and highly specialized species are more likely to go extinct than species characterized by large populations.

· Species in which population sizes gradually decrease, the so-called “population decline paradigm.” In normal cases, populations have a tendency to regenerate themselves, so a population showing persistent signs of decline is likely to disappear unless the cause of the decline is identified and eliminated.

· Species with low population densities. Species with an overall low population density, if the integrity of their range has been disrupted by human activity, will be represented in low numbers in each fragment. The population size within each fragment may be too small for the species to survive. It is beginning to disappear throughout its entire range.

· Species that require large habitats. Species in which individuals or social groups They forage over large areas and are prone to extinction if part of their range is destroyed or fragmented by human activity.

· Types of large sizes. Compared to small animals, animals large size usually have larger individual territories. They need more food and are more often hunted by humans. Large predators are often exterminated because they compete with humans for game, sometimes attack domestic animals and people, and they are also the object of sport hunting. Each guild has the most species large species- the largest predators, the largest lemur, the largest whale - are most susceptible to extinction.

· Species incapable of dispersal. During natural course natural processes environmental changes force species to adapt either behaviorally or physiologically to new conditions. Species unable to adapt to a changing environment must either migrate to more suitable habitats or face extinction. The rapid pace of human-induced change often outpaces adaptation, leaving migration as the only alternative. Species that are unable to cross roads, fields and other human-disturbed habitats are doomed to extinction as their “native” habitats are transformed by pollution, the invasion of new species or due to global climate change. Low dispersal ability explains why 68% of shellfish species among aquatic invertebrates in North America have disappeared or are at risk of extinction, in contrast to dragonfly species, which can lay eggs while flying from one body of water to another, so for them the figure is 20%.

· Seasonal migrants. Seasonally migratory species are associated with two or more widely separated habitats. If one of the habitats is disturbed, the species cannot exist. Survival and reproduction of billions of songbirds, 120 species migrating between Canada and South America, depends on the availability of suitable habitats in both areas. Roads, fences or dams create barriers between essential habitats that some species need to complete their entire life cycle. For example, dams prevent salmon from moving up rivers to spawn.

· Species with low genetic diversity. Intrapopulation genetic diversity sometimes allows species to successfully adapt to a changing environment. When a new disease, new predator, or other change emerges, species with low genetic diversity may be more likely to go extinct.

· Species with highly specialized requirements for an ecological niche. Some species are adapted only to unusual types of rare, scattered habitats, such as limestone outcrops or caves. If the habitat is disturbed by humans, this species is unlikely to survive. Species with highly specialized dietary requirements are also at particular risk. A striking example of this is the species of mites that feed only on feathers certain type birds. If a bird species disappears, so does the feather mite species.

· Species living in stable environments. Many species are adapted to environments whose parameters vary very little. For example, living under the canopy of a primary tropical rainforest. Often such species grow slowly, have low reproductive rates, and produce offspring only a few times in their lives. When rain forests cut down, burned, or otherwise altered by humans, many species living here are unable to survive the resulting changes in microclimate (increased light, decreased humidity, temperature fluctuations) and the emergence of competition with early successional and invasive species.

· Species that form permanent or temporary aggregations. Species that form clusters in certain places. For example, the bats At night they feed over a large area, but usually spend the day in a specific cave. Hunters who come to this cave during the day can collect the entire population to the last individual. Herds of bison, flocks of passenger pigeons and schools of fish are aggregations that were actively used by humans, until the complete depletion of the species or even extinction, as happened with the passenger pigeon. Some species of social animals cannot survive when their population numbers drop below a certain level because they can no longer forage, mate, or defend themselves.

· Species hunted or collected by humans. The prerequisite for the extinction of species has always been their utilitarianism. Overexploitation can rapidly reduce the population size of species of economic value to humans. If hunting or gathering is not regulated by law or local customs, species may become extinct.

These characteristics of endangered species are not independent, but are grouped into larger categories. For example, species of large animals tend to form populations with low densities and large ranges—all characteristics of endangered species. Identifying such characteristics helps biologists take early action to conserve species especially in need of protection and management.

QUESTIONS FOR SELF-CONTROL

1. What do you know about the rate of species extinction and how does this problem relate to the concept of biological diversity?

2. What is the rate of extinction of species at the present stage?

3. List the most significant reasons for the decline in biodiversity caused by human activities.

4. What causes the destruction and fragmentation of habitats of living organisms? What are the consequences of these phenomena?

5. What is the “edge effect”?

6. What are the reasons for the degradation of the living conditions of plants and animals?

7. What are the main sources of habitat pollution?

8. What does overexploitation of plant and animal resources lead to? Give examples.

9. Define the concepts of “invasive species” and “introduction”.

10. List the factors underlying the introduction of species.

11. What are the three basic principles of epidemiology that should be relied upon when breeding species in captivity and managing rare species?

12. What is the reason for the unequal probability of species extinction?