• Biodiversity or Biological diversity, is the term used to describe
the variety of plants and animals and other living things found
• Biodiversity is the variability among terrestrial, marine and
other aquatic living organisms and their ecosystems. This
includes diversity within species (genetic diversity), between
species and of ecosystems.
• For example, desert plants and animals have different
characteristics and needs than those in the mountains. Also
the desert and mountain ecosystems are different from each
other with different weather, vegetation etc.
Benefits of Biodiversity
• Biodiversity has led to the development of drugs that come from
plants, animals, or microbes. Around half of all drugs on the market
in the United States are derived from plants, animals, or microbial
Biodiversity also helps humans in the agricultural, business, and
• In agriculture, diversity among crops helps to reduce weakness to
disease and to improve overall crop performance.
One of the reasons biodiversity is important is because it helps to
keep the environment in a natural balance. An ecosystem which is
species-rich is more strong and adaptable to external pressures than
one in which the range of species is limited. In a system where
species are limited, the loss or temporary reduction of any one could
disrupt a complex food chain with serious effects on other species in
that same system.
Threats to Biodiversity
• Habitat loss and degradation
• Alien invasive species
• Climate change and
• Habitat loss in the terrestrial domain has been caused mainly
by the expansion of agriculture: more than 30% of land has
been converted for agricultural production.
• Wetlands in particular have faced a 50 per cent loss in the 20th
• Freshwater ecosystems are severely affected by fragmentation
• Bottom habitats have been degraded as a consequence of
bottom fishing with nets and other destructive fishing
• Overexploitation of wild species to meet consumer demand threatens
biodiversity, with unregulated overconsumption contributing to declines
in terrestrial, marine and freshwater ecosystems.
• major exploited groups include
• plants for timber, food and medicine
• mammals for wild meat and recreational hunting
• birds for food and the pet trade; and
• amphibians for traditional medicine and food
• The threat to vertebrates from overexploitation is particularly severe,
especially due to demand for wildlife and wildlife products from East
• Globally, utilized vertebrate populations have declined by 15 per cent
• Similarly, the extinction risk of utilized bird species increased during
1988–2008, partly due to overexploitation.
• In the marine systems, capture fisheries more than quadrupled their
catch from the early 1950s to the mid-1990s.
• Overfishing is also a problem in freshwater wetlands
Invasive alien species
• Invasive alien species threaten native biodiversity and are spreading
through both deliberate and unintentional introductions as a
consequence of increasing levels of global travel and trade.
• Poorly planned economic introductions, air transport, water from
ships, trade in pets, garden plants and aquarium species, are
significant pathways for the dispersal of invasive species.
• Invasive alien species affect native species principally through
predation, competition and habitat modification.
• Data from Europe show that the number of alien species has
increased by 76 per cent since 1970
• In another study, invasive alien species were a factor in more than
50 per cent of vertebrate extinctions where the cause was known,
and were the sole cause of 20 per cent of extinctions
• Climate change is an increasingly important threat to species
and natural habitats. There is widespread evidence that
changes in phenology, including the timing of reproduction
and migration, physiology, behaviour, morphology, population
• density and distributions of many diferent types of species are
driven by climate change.
• Pollutants such as pesticide and fertilizer effluents from
agriculture and forestry, industry including mining and oil or
gas extraction, sewage plants, run-of from urban and
suburban areas, and oil spills, harm biodiversity directly
through mortality and reduced reproductive success, and also
indirectly through habitat degradation
• Additional threats to biodiversity include changes in fire
regimes, problematic native species (Figure 5.1) and negative
influences from human activities.