Anyone even the slightest bit interested in wildlife and the environment knows of the impact that one animal species -- human beings -- has had on all other living things. Most of this impact has been negative. Human beings have hunted animals for pure pleasure; and we've killed thousands of animals by taking over their homes and their habitats to make way for agriculture and for our ever-expanding cities. We've cut down millions of trees to make furniture, and killed huge whales to manufacture candles and pet food.

All this killing and destroying could be excusable if it was for our survival, or even to maintain a basic standard of living. But the destruction has taken place so that humans can have lifestyles of luxury and indulgence. Our constant desire to consume more and more, while denying other species their due, has resulted in pesticides, dams, damage to coral reefs, and overfishing. Humans like to believe that anything that nature produces is for their use. Scientists estimate that people use 40% of the earth's produce, leaving 60% for all the other species combined.

As a result of our excessive use of fossil fuels we are changing the environment so rapidly that the earth will become unliveable for a number of species.

Environmentalists are already beginning to think of human beings as a kind of 'disease' or 'pest' that's eating up the earth's resources.

So, if there were no people would the planet be restored to good health? How long would it be before the earth recovered its health? Would it, in fact, ever fully recover? Or have we pushed it beyond recovery?

A story in the October issue of the reputed science magazine New Scientist gave a recovery timeline for the earth once people were out of the way. It said that the earth would indeed begin to heal itself, and that after a while natural systems would revert to their pre-human state with very few changes. That the air, soil and water would slowly become cleaner as pollutants faded away.

The first noticeable change would be light pollution. Light is one of the strangest indicators of human presence and there are very few places in the world where human-created light is not visible in the darkest of nights. In a day or two, blackouts would become common as power stations shut down due to lack of fuel. Because of the way they are designed, power stations need constant monitoring. Once people stop monitoring them they would simply break down and stop producing electricity. Lack of electricity would mean not just no lights but also the end of water pumps, sewage treatment plants and other electric machines.

Modern buildings are built to last 60 years, bridges 120 years, and dams 250 years. But these lifespans are dependent on maintenance; someone has to keep cleaning them, painting them, and fixing small problems before they get bigger. If the maintenance stops, the lifespans of these things are shortened.

Forests, oceans, prairies and rivers will recover, though at different speeds depending on where they are. Those in hotter, wetter areas like the tropics will bounce back more quickly than those in colder, more arid regions. Places where there are still lots of native species will recover faster than those without. For example, wherever native forests have been replaced by single-tree-species plantations it will take a lot longer (several generations of trees) to return to a natural state. This is also true of large agricultural areas consisting of huge farms of rice, wheat and other single crops.

Domestic animals and plants will become part of the new reverted ecosystems. Highly domesticated species such as cows, horses and dogs, bred over centuries to meet our needs, will probably evolve back towards hardier, less specialised forms and will exist in smaller numbers, thanks to diseases and the presence of predators.

In rivers, lakes and oceans fish populations will gradually recover from drastic overfishing, though it will take a while for fish like cod to return in large numbers. The good news is that coral and other bottom-dwelling organisms and deepwater reefs will recover in areas that are now just underwater wastelands.

As soon as human beings disappear, pollution from cars and factories will cease, and, with time, depending on the individual chemistry of each particular pollutant, will disappear. Nitrogen and sulphur gases, considered dangerous to humans now, will leave the atmosphere in a few weeks. Others, like pesticides, dioxins and refrigerants, will take longer to break down and will last a few decades.

The nutrients we dump into waterbodies, especially nitrates and phosphates from sewage and fertilisers, which kills lakes and rivers by choking them with algae that grow using these nutrients, will clear away within a few decades.

Carbon dioxide, the biggest worry because of its contribution to global warming, will take longer to disappear. It will be absorbed into the ocean but will take around 1,000 years. There will still be CO2 left in the atmosphere, continuing to influence the climate, more than 1,000 years after human beings disappear from the earth.

Overall, it will only take a few tens of thousands of years before traces of human presence begin to disappear. Within a few million years, erosion and possibly another ice age or two will have gotten rid of even the faintest trace of human beings.

One worrying problem for environmentalists has always been nuclear powerplants: will they continue to spread their poisonous radioactive influence forever? Lack of maintenance will harm the 430-odd nuclear powerplants now operating globally. As cooling water evaporates or leaks away, reactor cores are likely to burn, explode or melt down, releasing large amounts of dangerous radiation.

The area around Chernobyl in the Ukraine -- which was abandoned after a nuclear accident 20 years ago and has no people living around it -- is proof of how fast nature can bounce back. Life was visible there just a short time after the disaster. First only rats, mice and feral dogs flourished. But soon their numbers dropped and native fauna started returning. Wildlife such as boar are 10-15 times as common in the Chernobyl area compared to outside it; even big predators like wolves now live in the area.

It seems that for nature to do her work, all it needs is for us to leave.

-- Manoj Nadkarni

InfoChange News & Features, October 2006