IT has been established beyond doubt now that greenhouse gases (GHG) pose serious threat to humans. Even then, it is true that without these gases the world would have been much too cold for comfort, unable to sustain life as we know it.

Many scientists today see the next 100 years as a time of traumatic environmental change. The United Nations Intergovernmental panel on Climate Change (IPCC) projects a rise in average global temperature of about 1 to 3.5 degrees Celsius by 2100. The report further says that this pattern of warming is a cause for concern, if not alarm. Because global temperatures are like bank rates, a small change can make a big difference.

A 1% rise in surface temperature could cause major disruptions in weather patterns that could produce flash floods and unexpected droughts. It could also melt the ice in the Arctic and Antarctica. Such ice melts may cause massive floods as rivers would be unable to cope with the tons of water released. At the same time, declining snow cover over the Himalayas could dramatically change the ecology of the region, causing desertification of the fertile mountain valleys. That could raise sea levels, with catastrophic consequences to island nations. And this pattern of warming -- more in the Arctic than in the equator, more in the night than the day, more in winter than summer -- fits that predicted by the supercomputer models about man-made climate change.

The impact of warming on water bodies is much more severe. IPCC projects that the world's oceans will rise anywhere from 15 to 95 cm by 2100. This may not sound much but figures at the high end of that scale would rob a low lying nation like Bangladesh of over 20% of its arable land. And in the US it could put the cities of New York, New Orleans and Florida Keys under water.

The worst has already started playing out -- seas have risen by 25 cm this century and more thermal expansion of sea water and glacier melting will push it up even further. Even at the low end of the scale mentioned above, rising waters would increase coastal erosion and heighten the damaging effects of hurricanes and coastal storms. Encroaching salt water has the potential to contaminate water supplies that coastal cities and farms depend on. Leaving aside the outright loss of land to the ocean, the threat of contaminated water supplies is perhaps the most serious problem faced by rising sea levels.

Inevitably, the adverse effect of climate change in areas like Bangladesh is grimmer. Research reports made public in the year 2002 indicated that 36,000 sq km in Bangladesh out of 1,47,550 sq km face an uncertain and grim future. This includes the Sundarbans, the biggest mangrove forest in the world, and the longest sea beach in Cox's Bazaar. The stark fact is that about 14,000 sq km in the coastal zone is just one metre above sea level.

Forests, home to two thirds of all species, temper climate and capture and store water. They store 40% of terrestrial carbon and can slow down build up of carbon dioxide in the atmosphere. Deforestation in mountains can worsen floods in grasslands or agricultural land below, as was the case in China and Madagascar and more recently in the hill region of Bangladesh.

Humans have hurt coastal and marine ecosystems directly by draining wetlands, cutting mangroves, trawling oceans for fish and destroying reefs and lagoons. Besides we damage these ecosystems indirectly as rivers transport the effluents and byproducts of agriculture, industry and urban areas to the coasts. Man-made climate change threatens all coastal areas, as melting glaciers send more water seaward and the warming and expanding of the oceans cause sea levels to rise.

This makes it abundantly clear for industrialised and affluent nations to set national or regional limits on the release of carbon dioxide, the chief suspect in global warming. Topping the list of offenders are China and the US, who are least bothered about the disasters this gas has been wreaking on the environment, even if they are not now immune from the catastrophes sweeping through their countries.

The situation, not only in Bangladesh but also around the world, is assuming serious proportions. Much of the world's land is too rocky, arid or salty for agriculture. Forests that have already been cut deserve protection -- they harbour the habitats of earth's endangered wild life. Fewer than two million species of animals, plants and micro-organisms have been identified. Yet tens of millions more may exist in oceans, rainforests and everybody's gardens. In fact, nature does not seek to make a connection with us, nature does not care if we live or die. The hard truth is that we can't survive without the oceans or the forests, for example, but they can do fine without us.

The extinction of forests has come in the wake of unprecedented population boom, especially in the Third World. Much of the land becomes less arable by the minute, assaulted by urbanisation, chemical pollution, desertification and overuse of limited water supplies. The exhaustion of land has created a new class of displaced persons known as “environment migrants.” While wars were fought over territory, the future may see “Green Wars” triggered by shortages of such basic resources as topsoil or water.

As a region loses its forests, it also loses its ability to trap and absorb water, and so run-off from the denuded woodland worsens the natural process of soil erosion. The result -- the world wears away 24 billion tons of topsoil a year. When dry areas are worn down by the wind and by intensive farming, the region may eventually become a sterile desert, a fate that has befallen 3% of the world's farm lands.

Now efforts are underway to right some of the wrongs. It is time to put environment or ecosystems at the centre of decision making in government. China, whose factories spew out poisons that fall as acid rain on its neighbours, must cut back on the use of coal and thus reduce sulphur dioxide emissions.

For poor countries as ours, the top priority should be to reduce rapid population growth and urbanisation. Overpopulation means overloading the earth's carrying capacity and that translates into diminishing resources for development and deteriorating quality of life.

In developing countries, which contain more than 80% of the world's 6 billion people, poverty, population growth and environmental damage are closely linked. The damage will accelerate as our population swells. In consequence, social unrest that we are witnessing now will erupt in more vicious form. In a bid to arrest such trends, especially in this age of globalisation and inter-dependence, all our activities have to be linked with sustainable development to create a hybrid concept of user-friendly economic growth

The message from either the Copenhagen or Cancun climate talks has not been very assuring. At the same time “Earth Day” seminars, meetings and rallies in our country, other than being just a slogan, must focus on the progress achieved in respect of providing clean water, protecting forests and reducing pollution.

The Cancun Deal in 2010 set a goal of limiting global warming to 2 degrees Celsius (3.6 degrees Fahrenheit) but does not identify the stepping stones to achieving this -- and the promises to curb GHG, the toughest issue of all, are only voluntary.

Issues where the Cancun talks could make progress include measures to avert deforestation which accounts for between 12 to 25% of global emissions of GHG. Countries could also give the formal go-ahead to a 'Green Fund' proposed as the main vehicle for providing up to $100 billion a year in aid to poor countries.

The writer is a columnist fo The Daily Star. E-mail: aukhandk@gmail.com