The state of the world?
Quite an eye-opening article from The Independent
An authoritative study of the biological relationships vital to maintaining life has found disturbing evidence of man-made degradation. Steve Connor reports
30 March 2005
Planet Earth stands on the cusp of disaster and people should no longer take it for granted that their children and grandchildren will survive in the environmentally degraded world of the 21st century. This is not the doom-laden talk of green activists but the considered opinion of 1,300 leading scientists from 95 countries who will today publish a detailed assessment of the state of the world at the start of the new millennium.
The report does not make jolly reading. The academics found that two-thirds of the delicately-balanced ecosystems they studied have suffered badly at the hands of man over the past 50 years.
The dryland regions of the world, which account for 41 per cent of the earth's land surface, have been particularly badly damaged and yet this is where the human population has grown most rapidly during the 1990s.
Slow degradation is one thing but sudden and irreversible decline is another. The report identifies half a dozen potential "tipping points" that could abruptly change things for the worse, with little hope of recovery on a human timescale.
The scale of the changes seen in the past few decades has been unprecedented. Nearly one-third of the land surface is now cultivated, with more land being converted into cropland since 1945 than in the whole of the 18th and 19th centuries combined.
The amount of water withdrawn from rivers and lakes for industry and agriculture has doubled since 1960 and there is now between three and six times as much water held in man-made reservoirs as there is flowing naturally in rivers.
Meanwhile, the amount of nitrogen and phosphorus that has been released into the environment as a result of using farm fertilisers has doubled in the same period . More than half of all the synthetic nitrogen fertiliser ever used on the planet has been used since 1985.
This sudden and unprecedented release of free nitrogen and phosphorus - important mineral nutrients for plant growth - has triggered massive blooms of algae in the freshwater and marine environments. This is identified as a potential "tipping point" that can suddenly destroy entire ecosystems. "The Millennium Assessment finds that excessive nutrient loading is one of the major problems today and will grow significantly worse in the coming decades unless action is taken," Dr Reid said.
"Surprisingly, though, despite a major body of monitoring information and scientific research supporting this finding, the issue of nutrient loading barely appears in policy discussions at global levels and only a few countries place major emphasis on the problem.
Between 1960 and 2000, the world population doubled from three billion to six billion. At the same time, the global economy increased more than six-fold and the production of food and the supply of drinking water more than doubled, with the consumption of timber products increasing by more than half.
Meanwhile, human activity has directly affected the diversity of wild animals and plants. There have been about 100 documented extinctions over the past century but scientists believe that the rate at which animals and plants are dying off is about 1,000 times higher than natural, background levels.
THE TIPPING POINTS TO CATASTROPHE
As population densities increase and living space extends into once pristine forests, the chances of an epidemic of a new infectious agent grows. Global travel accentuates the threat, and the emergence of Sars and bird flu are prime examples of diseases moving from animals to humans.
The introduction of an invasive species - whether animal, plant or microbe - can lead to a rapid change in ecosystems. Zebra mussels introduced into North America led to the extinction of native clams and the comb jellyfish caused havoc to 26 major fisheries species in the Black Sea.
A build up of man-made nutrients in the environment has already led to the threshold being reached when algae blooms. This can deprive fish and other wildlife of oxygen as well as producing toxic substances that are a danger to drinking water.
CORAL REEF COLLAPSE
Reefs that were dominated by corals have suddenly changed to being dominated by algae, which have taken advantage of the increases in nutrient levels running off from terrestrial sources. Many of Jamaica's coral reefs have now become algal dominated.
Overfishing can, and has, led to a collapse in stocks. A threshold is reached when there are too few adults to maintain a viable population. This occurred off the east coast of Newfoundland in 1992 when its stock of Atlantic cod vanished.
In a warmer world, local vegetation or land cover can change, causing warming to become worse. The Sahel region of North Africa depends on rainfall for its vegetation. Small changes in rain can result in loss of vegetation, soil erosion and further decreases in rainfall.