Box The Escalating Problem of Biodiversity Loss

The loss of biodiversity is tremendous and disturbing, and it continues to grow at an exponential rate (see Figure)—even though scientists for decades have been saying that species and ecosystems are important, that they provide invaluable goods and services, that they keep people fed and clothed and Earth habitable.

The Millennium Ecosystem Assessment, one of the most comprehensive scientific assessments of the world's biodiversity ever undertaken, came to this sobering conclusion:"Human actions are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity." The authors cited ample evidence to support their conclusion. For example:

• Virtually all of Earth's ecosystems have now been dramatically transformed through human actions. More land was converted to cropland in the 30 years after 1950 than in the 150 years between 1700 and 1850.

• Some 35 percent of mangroves have been lost in the last two decades in countries where

8 loo

ON X

1970 1975 1980 1985 1990

adequate data are available.

• Over half of the 14 biomes assessed have experienced a 20-50 percent conversion to human use, with temperate and Mediterranean forests and temperate grasslands being the most affected.

• There are approximately 100 well-documented extinctions of birds, mammals, and amphibians over the last 100 years—a rate 100 times higher than background rates.

• Some 12 percent of bird species, 23 percent of mammals, and 25 percent of conifers are currently threatened with extinction. In addition, 32 percent of amphibians are threatened with extinction, but information is more limited and this may be an underestimate.

Sociobiologist E.O.Wilson attributes the loss of biodiversity to five forces summarized in the acronym HIPPO—habitat loss, invasive species, pollution, population growth, and overexploitation of species for consumption (essentially over-consumption).While he is correct in singling out each of these forces, they are in many ways interconnected: the first three are byproducts of the last two.They are essentially the result of human numbers multiplied by human greed.And given that human population is expected to go from 6 billion in 2000 to 9 billion in 2050 and that per capita consumption of everything from water and energy to oil and food is growing at practically exponential rates, the pressures on biodiversity are likely to become unbearably intense.

1995 2000 Source: See endnote 1.

Source: MA

Terrestrial species

Source: MA

Terrestrial species

All vertebrate species -(Living Planet Index)

The Living Planet Index is an indicator of the state of the world's biodiversity: it measures trends in populations of vertebrate species living in terrestrial, freshwater, and marine ecosystems.

Freshwater^ species

All vertebrate species -(Living Planet Index)

The Living Planet Index is an indicator of the state of the world's biodiversity: it measures trends in populations of vertebrate species living in terrestrial, freshwater, and marine ecosystems.

Freshwater^ species

0 0

Post a comment