Friday, November 26, 2010

Predicting The Future Of Biodiversity: Global-Scale Extinctions Will Increase Strongly

The loss of biodiversity will continue in the 21st Century. Global-scale extinctions will increase strongly, the average species abundance1 will decline and their distribution will be disturbed. Scientists thought until recently that the complexity of biodiversity made it unfeasible to predict future trends. Now, however, like the climatologists, life science specialists are able to predict future situations.

A group of international experts, including several IRD researchers, have just published a compilation of global-scale quantitative scenarios depicting possible changes in biodiversity. In spite of a degree of uncertainty in the models elaborated, the possible trends converge. If the processes of human and economic development do not change radically, the Earth is heading for disaster. With changes in land use, in climate and overexploitation of natural resources, humans activities are central to the major threats to biodiversity. The scenarios developed nevertheless point to possible lines of action.

Requin Baleine

Credit: © IRD / Pierre Laboute

Like their counterparts in the IPCC (Intergovernmental Panel on Climate Change) on the future climate, life sciences specialists can now attempt to predict changes in the biodiversity. For that domain, the future is scarcely any brighter. Biological diversity will continue to decline throughout the 21st- Century. A group of international experts2, including several IRD scientists, recently published a summary compilation of model scenarios depicting the worldwide scale changes and developments in biodiversity. All the predictions point to the same conclusion: increase in the number of global extinctions, a fall in the abundance of species and substantial changes in their distribution.

Biodiversity in crisis

Even the most optimistic scenarios predict the decline, even the extinction, of many species over the next century. Most plants and animals will be subject to regression of their distribution area or abundance. The research team announces, for example, that the overall abundance of terrestrial species could diminish from 10 to 20 % during the first half of the century. In the “biodiversity crisis”, it is a change in composition of communities more than the disappearance of species which will be the most critical factor for humans.

Causes and consequences

The main factors behind loss of biodiversity are the degradation and destruction of natural habitats, climate change and overexploitation of biological resources. Changes in land use, brought on for instance by urbanization or the conversion of equatorial forest into pasture and arable land, is therefore the principal threat to biodiversity. It affects firstly the countries of the South, such as Central and Southern Africa, the Atlantic areas of South America and part of South-East Asia. Climate change is also severely upsetting habitats and disturbing ecosystems. It leads for example to invasion of Arctic tundra by boreal forest, which is shifting towards the Poles as the climate warms up. Other threats are acidification of oceans, rise in sea level and pollution which alter the coral reefs and destroy a significant number of coastal ecosystems. Overfishing leads to a decline in the top predators, such as tuna and shark, thereby completely disturbing the marine food chain.

The resulting loss of biodiversity can have strong effects on human well-being and development. For example, irreversible degradation of littoral habitats exposes coasts to heightening risk of damage from waves and storm surges and loss of fishing productivity. Projections indicate that most factors behind erosion of diversity will persist and that climate change will amplify this trend over the next century.

Real progress is possible

The research team nevertheless shows that means for controlling the decline exist. Limiting deforestation can help counter the trend. The researchers forecast that, depending on the measures taken now, in the most advantageous cases, there will be an overall world increase in forest cover between now and 2030 of about 15%, amounting to 10 million km², equivalent to the surface area of Canada or China. Conversely, the worst scenario indicates a reduction by over 10% of the surface area of des forests.

Increasing the efficiency of agriculture, reducing greenhouse gas emissions, large-scale reforestation, reinforcement of fishing regulations, creation of both terrestrial and marine nature reserves, are all measures that could also enable humans to lessen their impact on the biodiversity.

These optimistic scenarios strive to remain coherent with the economic constraints and populations’ use of resources. Nevertheless, they indicate an imperative for radical changes in the present mode of development. In line with this, biodiversity specialists can now make predictions available to political decision-makers. Like the IPCC, an Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES)  is being formed. At national level, a wide-ranging programme was initiated in July 2010 aiming to continue the research and refine the models by the Fondation pour la Recherche sur la Biodiversité3, of which the IRD is founder member.

Number of individuals of a species per unit of surface area or volume.

These investigations were conducted by DIVERSITAS (international research programme on biodiversity) and the United Nations Environment Programme World Conservation Monitoring Centre for the Secretariat of the Convention on Biological Diversity. This summary was carried out by research scientists from the Université Paris-Sud, the Universidade de Lisboa and Universidade de Évora au Portugal, the IRD, the Departamento de Biodiversidad y Biología Evolutiva in Madrid, Spain, from the Netherlands Environmental Assessment Agency, the PNUE-WCMC, Imperial College London and the University of East Anglia in the United Kingdom, Stockholm University in Sweden, the Universidad Nacional Autónoma de México in Mexico, University of Maryland, the Hawaii Pacific University, from the Joint Global Change Research Institute, The Nature Conservancy and from the Pew Environment Group in the United States, the Secretariat of the Convention on Biological Diversity and the University of British Columbia, Canada and CSIR Natural Resources and Environment in South Africa.

Contacts and sources: 
Citation: Pereira H.M., Leadley P. et al., Scenarios for Global Biodiversity in the 21st Century, Sciencexpress , 26 Octobre 2010. DOI: 10.1126/science.1196624 

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