Satellite map reveals man's destructive nature

Unique atlas shows that humans have radically altered half the surface of the Earth

A new scientific picture of the world, showing how man has left an indelible mark on the planet that is visible from space, was published yesterday by scientists who warned that the Earth was undergoing an unprecedented transformation.

A new scientific picture of the world, showing how man has left an indelible mark on the planet that is visible from space, was published yesterday by scientists who warned that the Earth was undergoing an unprecedented transformation.

The map, compiled from satellite images, shows almost a quarter of the Earth's surface has been entirely transformed, either by being covered overby roads and buildings or ploughed up for crops. Another quarter has been exploited to a lesser degree, but in a way that has completely altered its natural state.

A rapidly growing human population, rising economic expectations, continual decline in natural resources and increasing pollution by industrialised countries are leading to a crisis of epic proportions.

This stark warning is contained in a new atlas of the world showing how humans have had a devastating impact on the natural environment. The report, compiled by the American Association for the Advancement of Science (AAAS), was published on the opening day of its annual meeting in San Francisco.

"We have become a force of nature comparable to volcanoes or to cyclical variations in the Earth's orbit," the report warns. "As we enter the third millennium, the destiny of the planet is in our hands as never before, yet they are inexperienced hands. We are modifying ecosystems and global systems faster than we can understand the changes and prepare responses to them."

The main satellite map in the AAAS Atlas of Population and Environment shows the full extent of human influence. The swath of pink, denoting complete transformation, covers not only the developed world of North America and Europe, but vast areas of Asia and Africa. No continent except Antarctica is unscathed.

"Humans are perhaps the most successful species in the history of life on Earth. From a few thousand individuals some 200,000 years ago, we passed 1 billion around 1800 and 6 billion in 1999. Our levels of consumption and the scope of our technologies have grown in parallel with, and in some ways outpaced, our numbers," the report says. "But our success is showing signs of overreaching itself, of threatening the key resources on which we depend. Today our impact on the planet has reached a truly massive scale. In many fields our ecological footprint outweighs the impact of all other living species combined.

"We have transformed approximately half the land on Earth for our own uses -- around 11 per cent each for farming and forestry, and 26 per cent for pasture, with at least another 2 to 3 per cent for housing, industry, services and transport. The area used for growing crops has increased by almost six times since 1700, mainly at the expense of forest and woodland," the report says.

Images from the Advanced Very High Resolution Radiometer satellite, operated by Nasa and the US Geological Survey, yielded the principal map on human transformation of the land, said Lars Bromley of the AAAS's Directorate for International Programs.

"You can determine whether something is paved over, whether something is bare soil, a ploughed field, or whether it's normal land cover," Mr Bromley said. "You can detect a lot of the sources of pollutants, basically from the northern hemisphere. When people see the extent of the transformation they are surprised."

Past attempts to estimate global land usehave been hindered by the lack of full geographical coverage, which is not a problem with a polar-orbiting satellite, Mr Bromley said. "By getting this eye-in-the-sky view you can prove that ... this cropland is far more extensive than anybody recognised."

The atlas shows the extent to which soil erosion has affected a substantial part of the Earth's surface that has gone under cultivation and then been abandoned. "Worldwide, an estimated 12 million hectares of croplands fall out of use for this reason each year. Economists have estimated the value of this lost soil, in terms of nutrients and water-holding capacity, at about $400bn," the report says.

Fresh water has also been degraded. "Chronic or acute water shortage is increasingly common in many countries with fast-growing populations, becoming a potential source of conflict," the report says. "The distribution of water resources around the globe is highly unequal ... Canada has more than 30 times as much water available to each citizen as China.

"Today it is estimated that 31 countries with 8 per cent of the world's population - mostly in Africa and the Middle East - have water shortages. By 2025 the figure is likely to have risen to 48 countries and 35 per cent of population ... The crisis is likely to be worsened by the deteriorating quality of water, polluted by industrial wastes and sewage discharges, and spreading diseases such as cholera and schistosomiasis."

The AAAS report concludes that humans have:

* Regulated the flow of about two-thirds of all rivers on Earth, creating artificial lakes and altering the ecology of existing lakes and estuaries;

* Fished two-thirds of marine fisheries to the limit or beyond and altered ecologies of many marine species. In 100 years we have destroyed half of coastal forests and irrevocably degraded a tenth of coral reefs;

* Contributed 50 per cent more to the nitrogen cycle than all natural sources combined, leading to the impoverishment of forest soils and forest death, and at sea to the development of toxic algal blooms and expanding "dead zones" devoid of oxygen;

* Released toxic metals into the biosphere through mining and processing that would otherwise have remained safely locked in stone;

* Had an incalculable effect on biodiversity. The 484 animal and 654 plant species recorded as extinct since 1600 are only "the tip of a massive iceberg";

* Become a major force of evolution, not just for the "new" species we breed and genetically engineer, but for the thousands of species whose habitats we modify, consigning many to extinction.

"In this unprecedented situation, the need to be fully aware of what we are doing has never been greater," the report says. "We need to understand the way in which population, consumption and technology create their impact, to review that impact across the most critical fields, and to find ways of using our understanding of the links to inform policy."