Biodiversity Overview

Biological diversity or biodiversity is a term used to describe variety and variability among living organisms and the ecological complexes in which they occur (source. State of the Environment in Zambia 2000, UNEP Global Biodiversity Assessment, 1995).

This page aims to provide an insight on biodiversity in general and answers some questions that may arise on this subject.

What is biodiversity?
How much biodiversity is there?
Why is biodiversity so important?
Is biodiversity threatened and why?
 

What is biodiversity?

Biodiversity is the shortened form of two words "biological" and "diversity." It refers to all the variety of life that can be found on Earth (plants, animals, fungi and micro-organisms) as well as to the communities that they form and the habitats in which they live.

The Convention on Biological Diversity (CBD) gives a formal definition of  biodiversity. Article 2 of the Convention states that:   "biological diversity means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems".

Biodiversity is not only the sum of all ecosystems, species and genetic material. Rather, it represents the variability within and among them. It can be distinguished from the expression "biological resources", which refer to the tangible components of ecosystems. Biological resources are real entities (a particular species of bird, a wheat variety growing in a field, oak wood, etc.) while biological diversity is rather an attribute of life (the variety of bird species, the genetic variability of wheat around the world, forest types, etc.).

Biological diversity is often understood at three levels:

1. Species diversity refers to the variety of different species (plants, animals, fungi and micro-organisms) such as palm trees,     elephants or bacteria;
2. Genetic diversity corresponds to the variety of genes contained in plants, animals, fungi and micro-organisms. It occurs within a species as well as between species. For example, poodles, German shepherds and golden retrievers are all dogs, but they all look different;
3. Ecosystem diversity refers to all the different habitats - or places - that exist, like tropical or temperate forests, hot and cold deserts, wetlands, rivers, mountains, coral reefs, etc. Each ecosystem corresponds to a series of complex relationships between biotic (living) components such as plants and animals and abiotic (non-living) components which include sunlight, air, water, minerals and nutrients.

How much biodiversity is there?

Estimates of the total number of species range from 7 to 100 million, with a probably good estimate being about 13 to 15 million species. Up to this day, only about 1.75 million living species have been identified and described scientifically. Many new species continue to be discovered each year, most of them invertebrates. During the nineties, the number of newly described species averaged 13,000 per year.

The table below shows approximate numbers of species in major groups (UNEP, Global Biodiversity Assessment, 1995):

Why is biodiversity important?

The natural environment provides the basic conditions without which humans could not survive. This seems intuitive enough: we need to breathe, eat, drink and shelter ourselves and we get all this from the natural world.

Ecological importance:

•  trees provide habitat and food for birds, insects, other plants and animals, fungi, and micro-organisms;
   insects, bats, birds, and other animals serve as pollinators;  
• parasites and predators act as natural population controls;
•  various organisms, such as earthworms and bacteria, are responsible for recycling organic materials and maintaining the productivity of soils; 
• green plants remove carbon dioxide from the atmosphere and replenish it with oxygen. Forests, for example, are particularly important "sinks" for the absorption of carbon dioxide and thus are key factors in reducing global climate change;
• wetlands serve as sponges to reduce the impacts of floods and to cleanse streams by filtering sediments, nutrients, and contaminants from inflowing waters.

The interaction of all these natural processes forms a complex web of life. If any part of this web suffers or breaks downs, the future of the other parts is threatened. Humans are in many cases degrading and destroying the ability of biological diversity to perform the services mentioned above.

Economical importance of biodiversity:

• Food: species are hunted (e.g. antelopes, birds), fished (e.g. cod, tuna fish), and gathered (e.g. fruits, berries, mushrooms), as well as cultivated for agriculture (e.g. wheat, corn, rice, vegetables) and aquaculture (e.g. salmons, mussels). It is interesting to know that, of the about 80,000 available comestible plants, humans use less than 30 to satisfy 90% of our planet's alimentary needs;
• Fuel: timber and coal are only two examples of natural resources used to produce energy;
• shelter and warmth: timber and other forest products (e.g. oak, beech, pine) are used as building materials and for shelter. Fibers such as wool and cotton are used to make clothes;
• Medicines: both traditional medicines and processed drugs are obtained from biodiversity: penicillin is produced by a mould, codeine is obtained from poppies, digitalis from foxglove and quinine from the bark of cinchona trees;
• other goods such as paper and pencils come from raw materials provided by the Earth's diversity.

Indirect services:

• Clean and drinkable water: only a small amount - about 1% - of the water on our planet is usable directly. The rest is either salty (97%) or frozen (2%). Forests around the world filter our usable water again and again, constantly replenishing the water we use for drinking, bathing, and growing crops;
• Air to breathe: plants around the world take carbon dioxide out of the air and put oxygen into it - oxygen that almost all creatures need to breathe;
• Fertile soils: micro-organisms recycle the soil's organic matter and maintain its fertility;
• Pollination: insect, bird and bat species carry pollen from one plant to another (or from one part of a plant to another), thus fertilising fruit crops and flowers.

Cultural importance of biodiversity:

Plants and animals are often used as symbols, for example in flags, paintings, sculptures, photographs, stamps, songs and legends.
Finally, biodiversity is also beautiful: it is a pleasure to see and smell flowers in a field, to listen to birds singing, etc.

Is biodiversity threatened, and why?

It is often the loss of big mammal species that catches most our attention: we are deeply touched of the disappearance of charismatic animals such as pandas, tigers or elephants, but we are less aware that many less conspicuous organisms are disappearing fast.

Today, species and habitats are becoming extinct or disappearing at top speed. Why? The main reasons are listed below:

• Habitat loss and destruction is usually a direct result of human activity and population growth. It is a driving force in the loss of species, populations, and ecosystems. When people cut down forests, dig mines, build cities, or make roads, they destroy habitats. When the habitats become smaller, less food and shelter are available. As a result, species living in these habitats compete with each other and with humans for limited resources. Since their populations are so small, they have fewer mates with whom to have offspring, diminishing the genetic diversity of their populations. Smaller habitats are like islands, isolated from each other, and species have greater difficulties migrating from one to another, as less suitable pathways are available;
• The introduction of alien (exotic or non-native) species can disrupt entire ecosystems and have a major impact on populations of native plants or animals. The invaders can affect native species by eating them, infecting them, competing with them, or mating with them. Invasion can happen through many different ways: seeds catch on people's clothes, rats hitch-hike on ships, marine species are transported around the world through ballast water from ships and insects can be introduced with the international trade for food or timber. The numbers of species introduced to areas in which they are not native are expected to increase as the scale of international trade, transportation and tourism continues to grow;
• Human-generated pollution and contamination (e.g. acid rain, oil spills, human waste, nuclear waste, over use of pesticides) can affect all levels of biodiversity;
• population growth: over 6 billion people live on Earth. More and more resources are used for food, water, medicine, clothes, shelter and fuel. This leaves fewer resources for the Earth's species and habitats;
• Over-exploitation (over-hunting, over-fishing or over-collecting) of a species or population can lead to its disappearance. Many of the world's natural resources are being used by humans faster than they can replace themselves. Commercial fish such as cod are over harvested, while species like dolphins and sea turtles often die in fishing nets. People buy wildlife and wildlife products to use as pets, medicines, gourmet foods or decorative objects;
• Global climate change will alter environmental conditions. As humans burn more fossil fuels like oil and coal for energy, more carbon dioxide enters the atmosphere. Carbon dioxide - or CO₂ - acts like a greenhouse, letting sunlight and heat into the lower atmosphere, but not letting heat back out. Other gases, including methane and nitrous oxide, released to the atmosphere by human activities, also contribute to global warming. As a result, average yearly temperatures on Earth have risen. Changes in the climate will modify the ecosystems in which many species - including humans - live. Some species and populations may be lost if they are unable to adapt to the new weather conditions or relocate to adequate habitats while other species - such as certain diseases and pests - may flourish and expand their ranges.