The variety of natural life forms, whether eco-regions, habitats, species or gene pools, is being endangered by human activity. This biodiversity ensures the regeneration of harvested resources and the maintenance of ecological processes, whether as a vital part of world heritage or for its own sake. It also provides resources for the development and improvement of domesticated crops and livestock, for recreation and tourism, and for research and education.
At the broadest level, biodiversity loss is driven by economic systems and policies that fail to value properly the environment and its resources, legal and institutional systems that promote unsustainable exploitation, and inequity in ownership and access to natural resources, including the benefits from their use. While some species are under direct threat, for example from hunting, poaching and illegal trade, the major threats come from changes in land use leading to the destruction, alteration or fragmentation of habitats.
Steps to achieve the conservation and sustainable use of biodiversity, and to minimise the adverse impacts of activities are necessary, but not sufficient, to address the loss of biodiversity. Underpinning the crisis is a complex array of inter-related social, economic, political and demographic factors. These include institutional failures to regulate the use of biological resources; economic systems that fail to recognize the true value of biodiversity; inequity in the ownership, management and flow of benefits from the conservation and use of biological resources; high levels of poverty; and a lack of knowledge about the way in which natural systems function.
Ultimately, human impacts on biodiversity depend upon two key factors: the number of people using natural resources; and the rates at which they consume those resources. Increasing human populations and unsustainable rates of resource consumption both lead to a growth in demand for natural resources, and therefore an increase in the impact on biodiversity. Because the natural resource base is limited, it is important to consider ways in which a balance can be struck between the use of resources, and the capacity of ecological systems to renew resources and to absorb wastes.
All species, as well as all individuals within a species, have a finite life span and thus changes in biodiversity are inevitable. Accelerated and enhanced reduction in diversity at gene, species and ecosystem level, however, is not only intrinsically undesirable but a significant threat to human material welfare because it implies reduced ability of ecosystems to provide key products and services.
The main levels of diversity of concern are: ecosystem diversity (the number and frequency of different communities of organisms and their environments); species diversity (the number and frequency of different species); and genetic diversity (meaning both genetic variability and the number and frequency of genetically distinct populations).
The energy and transport sectors have a global and regional impact on biodiversity through climate change and acidification. Additionally, the development of infrastructures for transport and for energy production may have a more local impact on biodiversity.
Niger has lost 80 per cent of its freshwater wetlands during the past two decades, two-thirds of Asian wildlife habitats have been destroyed with the most acute losses in the Indian sub-continent, China, Vietnam and Thailand and, in the Latin American region, the average annual deforestation rate during 1990-95 was 2.1 per cent in Central America and more than 1 per cent in Paraguay, Ecuador, Bolivia and Venezuela.
According to a 1999 report, in the USA, 37 percent of freshwater fish were at risk of extinction, 50 percent of crayfish and 40 percent of amphibians were emperiled, and 67 percent of freshwater mussels were extinct or vulnerable to extinction.