Biodiversity is the variety of life in an area. It includes species diversity (the number of species and their relative abundance), genetic diversity (the variety of alleles within a species) and habitat diversity (the range of habitats).Human activity reduces biodiversity at all three levels:
• Habitat loss and fragmentation: clearing forests, draining wetlands and building roads leave small, isolated patches that support fewer species and smaller populations.
• Agriculture: a monoculture replaces a mixed habitat with a single crop; removing hedgerows, spraying pesticides and herbicides, and fertiliser run-off causing eutrophication all reduce the number of species.
• Pollution, over-exploitation, invasive species and climate change add further pressure.Genetic diversity falls when populations become small, because alleles are lost by chance (genetic drift) and inbreeding becomes more likely. Selective breeding of crops and livestock has also narrowed the gene pool of domesticated species, so a single disease can devastate a crop.Loss of biodiversity matters because:
• ecosystems with more species are usually more stable and recover better from disturbance;
• wild species are sources of new medicines and of genes for crop improvement;
• ecosystems provide services such as pollination, clean water, flood control and carbon storage;
• many people argue that we have an ethical duty to protect other species.
• Habitat loss and fragmentation: clearing forests, draining wetlands and building roads leave small, isolated patches that support fewer species and smaller populations.
• Agriculture: a monoculture replaces a mixed habitat with a single crop; removing hedgerows, spraying pesticides and herbicides, and fertiliser run-off causing eutrophication all reduce the number of species.
• Pollution, over-exploitation, invasive species and climate change add further pressure.Genetic diversity falls when populations become small, because alleles are lost by chance (genetic drift) and inbreeding becomes more likely. Selective breeding of crops and livestock has also narrowed the gene pool of domesticated species, so a single disease can devastate a crop.Loss of biodiversity matters because:
• ecosystems with more species are usually more stable and recover better from disturbance;
• wild species are sources of new medicines and of genes for crop improvement;
• ecosystems provide services such as pollination, clean water, flood control and carbon storage;
• many people argue that we have an ethical duty to protect other species.