The Hindu Business Line : Earth’s loss

At the start of the millennium, the United Nations set a clear, measurable objective for biodiversity conservation. The target agreed on by the parties to the Convention on Biological Diversity (CBD) in 2002 set 2010 as the year by which a significant reduction in the rate of biodiversity loss should be achieved globally. Unfortunately, this target appears unlikely to be met.

Numbers of birds, animals, marine and freshwater creatures have dropped by more than a quarter since 1970, claims The Living Planet Index, a report commissioned by the WWF, the Zoological Society of London and the Global Footprint Network. The report says that between 1970 and 2005 land-based species fell by 25 per cent, marine species by 28 per cent and freshwater species by 29 per cent.

It shows that wild species and natural ecosystems are under pressure across all biomes and regions of the world.

Jonathan Loh, the editor of the report, says all the threats stem ultimately from human demands on the biosphere — the production and consumption of natural resources for food and drink, energy or materials, and the disposal of associated waste products — or the displacement of natural ecosystems by towns, cities and infrastructure. Further, the massive flows of goods and people around the world have become a vector for the spread of alien species and diseases. Natural habitats, especially in terrestrial ecosystems, are lost, altered or fragmented through their conversion for cultivation, grazing, aquaculture, and industrial or urban use.

River systems are dammed and altered for irrigation, hydropower or flow regulation, and even marine ecosystems, particularly the seabed, are physically degraded by trawling, construction and extractive industries.

Overexploitation of wild species populations is the result of harvesting or killing animals and plants for food, materials or medicine, over and above the reproductive capacity of the population to replace itself.

Invasive species — which have been introduced either deliberately or inadvertently from one part of the world to another and have become competitors, predators or parasites of indigenous species — are responsible for declines in many native species populations. This is especially relevant to islands and freshwater ecosystems, where invasive species are thought to be the main cause of extinction among endemic species, Loh emphasises.

Pollution is another important cause of biodiversity loss, particularly in aquatic ecosystems. Excess nutrient loading is a result of the increasing use of nitrogen and phosphorous fertilisers in agriculture, which causes eutrophication and oxygen depletion.

Toxic chemical pollution often arises from pesticide use in farming or aquaculture, from industry or mining wastes. One result of increasing carbon dioxide concentrations in the atmosphere is the acidification of the oceans, which is likely to have widespread effects on marine species, particularly shell and reef-building organisms.

Less significant in the past, but with the potential to become the greatest threat to biodiversity over the course of the next few decades, is climate change.

Already, impacts of climate change have been measured in arctic and alpine, as well as coastal and marine ecosystems such as coral reefs. The global extent of climate change will mean that no ecosystem on the surface of the Earth will be immune from rising air or sea temperatures or changing weather patterns.