BIODIVERSITY IN CRISIS

The most obvious manifestation of biodiversity loss is the extinction of species. This is a natural phenomenon: species have been going extinct since life began. Indeed, it is estimated that many more species have gone extinct than exist at present. What's worrying is the rate at which species are currently dying out: not since the demise of the dinosaurs (some 65 million years ago) has earth witnessed an 'extinction event' of such catastrophic scale.

Since the total number of species on earth can only be estimated, the exact rate of current species loss is difficult to gauge. The figure probably stands at between 50 and 150 extinctions per day. Working from the conservative estimate that earth is home to 10 million species in all, this means that between 0.2 and 0.6 percent of species are being lost every year. This rate is at least 10,000 times greater than the ‘background’ or natural rate of species extinction, as estimated using the fossil record.

The World Conservation Union (IUCN) has estimated that over 5,500 species of animals – including birds, mammals, reptiles, amphibians, fishes and invertebrates – are currently threatened with extinction, together with 6,700 species of higher plants.

Those considered vulnerable, threatened, or critically endangered include:

>> Close to 1,100 species of mammals (about 24 per cent of the total number).

>> Over 1,100 birds (around 12 per cent of known species).

>> Over 750 species of fish (49% per cent of total surveyed).

>> Around 290 species of reptiles (62 per cent of total number surveyed).

>> An estimated 157 species of amphibians (39 per cent of the total number surveyed).

Over 5,500 species of animals are threatened with extinction

The annual extinction rate is set to rise still further. Eminent biologist Edward O. Wilson has estimated that if current trends continue, a fifth of all species will go extinct within the next 30 years.

The picture is no more encouraging from an ecosystem perspective:

>> More than 50 per cent of the world’s wetlands have been drained.

>> Since 1950, some 3 billion hectares of forest cover – nearly half – has been lost. Each year, a further 16 million hectares of forest are destroyed.

>> Between 50 and 80 per cent of mangrove ecosystems have been destroyed.

>> Roughly one-third of the world’s coral reef systems have been destroyed or highly degraded.

>> One fourth of the planet’s topsoil has been lost.

>> 69 per cent of the world’s major fish stocks are either fully exploited, over-fished, depleted, or slowly recovering, and productivity has fallen in all but four of the 15 most important fishing regions.

>> Nearly 2 billion hectares of crop and grazing land are suffering from moderate to severe soil degradation.

Genetic diversity within species is also being eroded. This trend is especially alarming from an agricultural perspective. Since 1900, some three-quarters of the genetic diversity of cultivated crops has disappeared, together with nearly half of the gene pool of the wild relatives of domestic animals. The loss of genetic diversity matters because a large proportion of the world’s agricultural systems depend on the regular assimilation of wild genes to stay one step ahead of the threat posed by pests and diseases.

The main causes of biodiversity loss are considered under the following headings:

>> Habitat destruction
Ecologists estimate that an area of ten square miles contains twice as many species, on average, as an area of one square mile, suggesting that to reduce an area of ecosystem to a tenth of its original size will cause half its species to become extinct. Animals at the top of the food chain (lions, bears, etc.) require especially large habitats in order to maintain viable wild populations.

>> Invasive species
Ecosystems are fragile balancing acts, evolved over millions of years as an integrated whole. The sudden introduction to a given ecosystem of an alien species can severely disrupt its normal functioning – with disastrous consequences for native species. Such introductions are usually the result of human activities. The accidental introduction to the Black Sea of an Atlantic comb jellyfish species is a well-known example. These invaders have out-competed native fauna, and now comprise some 95 per cent of the Black Sea’s total biomass (a disaster for the local economy). In the US, meanwhile, the introduction of exotic species has been implicated in close to 70 per cent of the past century’s freshwater fish extinctions.

>> Pollution
The chemical contamination of fresh water, seawater and soils can lead to the disappearance of populations and species. Agricultural runoff, containing fertilizers and pesticides, can seep into aquifers and rivers eventually reaching the ocean. Once present in the food chain, contamination can have far reaching consequences such as in the case of the decreased barn owl population in the United Kingdom that resulted from the introduction of new rodenticides. Additionally, atmospheric pollution has contributed to accelerated climatic change with expected consequences including the disruption of species distribution and even extinction.

>> Over-harvesting
Many species have been harvested or hunted to rarity and beyond. Examples of such directly wrought extinctions include those of the passenger pigeon and the Carolina parakeet in the early part of the twentieth century. More recently, the Central African ‘bushmeat’ trade has placed mountain gorillas and chimpanzees under direct threat.

>> Climate change
Over the past century or so, global temperatures have risen by between 0.3 and 0.6°C (the largest increase in at least 1,000 years), due in large part to the increased presence in the atmosphere of 'greenhouse gases' from industrial processes. The effects of climate change have so far included a rise in sea levels of some 10-25 cm worldwide, a loss of glacier ice, changes in precipitation patterns, and an increased occurrence of extreme weather events. These fluctuations have disturbed seasonal cycles throughout the globe. It is feared that these changes are happening at too fast a rate for many species to adapt.

Despite that the growth of human societies is the prime mover behind every one of these five more immediate factors, biodiversity loss is not the inevitable result of social and economic growth and development. Environmental sustainability is possible. But there are a number of specific factors standing in the way of its widespread achievement. These factors originate in some of the most basic social, economic, political, cultural and historical features of society. They include:

>> Market and economic policy failures such as inappropriate regulatory mechanisms, harmful subsidies and incentives, inadequate economic valuation of biodiversity, the absence of local and global markets for biodiversity goods and services and the lack of clear environmental and development policies.

>> Social, political and institutional weaknesses such as unsustainable production and consumption patterns, poverty, lack of clear land use rights, uneven distribution of land ownership, poor governance, fragmented decision making, lack of political will, political unrest and wars.

>> Lack of knowledge of biodiversity’s importance, particularly among hose directly involved in the management of biodiversity and among economic and developmental decision-makers.

With these factors in mind, it is clear that just as humanity depends on biodiversity for its survival and development, the long-term survival of earth’s biodiversity will necessitate the achievement of sustainable human development.

Online resources:

The IUCN Red List of Threatened Species
The world’s most comprehensive inventory of the global conservation status of plants and animals.

NatureServe
Contains information on rare and endangered species and threatened ecosystems.

Biodiversity Conservation Information System

GLOBIO
Maps human effects on the biosphere.

Ecolynx: Information Context for Biodiversity Conservation
An integrated information package for biodiversity conservation that links data on threatened species and habitats with information about responses by society to threats to biodiversity.

Millennium Ecosystem Assessment
Contains peer-reviewed, policy-relevant scientific information on the condition of ecosystems, consequences of ecosystem change, and options for response.

 

>> Back to top