So far, there has been official silence on the possible environmental and social implications of an invasion of Iraq. Yet the possible damage to the environment, to communities and above all to civilians deserve urgent moral consideration before any decision for war is taken. Neither the British nor the US Governments have made any published effort to assess these risks, or to show why they are outweighed by the alleged benefits of invasion.

Of course, it is impossible to be certain what will happen in any war. No-one knows if it will be short or long, an easy victory for the US or a painful and bloody struggle. All attempts to assess risks are difficult and tentative at best. But we must still look carefully at what happened in previous conflicts, including the damage done by the 1991 Gulf War.

First, targeting industrial and military sites such as armaments factories and oil refineries is likely to lead to acute chemical pollution. A report on the Kosovo war by the United Nations Environment Programme concluded that military action resulted in no general 'ecological catastrophe', but resulted in "some serious hot spots where contamination by hazardous substances released during the air strikes poses risks for human health and the aquatic environment".

The UK Government has named nine sites in Iraq as involved in the production of biological and chemical agents. It can be assumed that these would be early targets for air strikes in the event of war.

During the 1991 war devastating damage was done to the oil industry in Kuwait. Iraqi forces destroyed more than seven hundred oil wells in Kuwait, spilling sixty million barrels of oil. Over ten million cubic metres of soil was still contaminated as late as 1998. A major groundwater aquifer, two fifths of Kuwait's entire freshwater reserve, remains contaminated to this day. Ten million barrels or oil were released into the Gulf, affecting coastline along 1500km and costing more than $700 million to clean up. During the nine months that the wells burned, average air temperatures fell by 10 degrees C as a result of reduced light from the sun. The costs of environmental damage were estimated at $40 billion. Estimates of the numbers likely to die as a result of the air pollution effects were put at about a thousand. Since Iraq has the second largest proven oil reserves of any nation on earth, the potential environmental damage caused by destruction of oil facilities during a new war must be enormous.

Other environmental effects of the 1991 Gulf War included destruction of sewage treatment plants in Kuwait, resulting in the discharge of over 50,000 cubic metres of raw sewage every day into Kuwait Bay.

Secondly, specific weapons likely to be used against Iraq will also create environmental damage. Top of the list of concern are depleted uranium (DU) projectiles.

Depleted uranium is very dense and is used in projectiles designed to pierce armour, reinforced bunkers and other similar targets. Depleted uranium projectiles create fragments and dust which release uranium oxide into the air. Estimates of the amount of depleted uranium used by allied forces in the first Gulf War range from 290 tonnes to 800 tonnes.

Decontamination requires removal of contaminated soil and treatment as radioactive waste. Thousands of hectares of Iraqi land could be contaminated. Decontaminating just 200 hectares at a US Army proving ground cost $4-5bn.

According to a 'threat paper' on Kuwait produced in secret by the UK Atomic Energy Authority and subsequently leaked, 50 tonnes of DU inhaled could cause up to half a million additional cancer deaths over several decades, a calculation based on International Committee on Radiological Protection risk factors. Internal DU exposure is acknowledged to cause kidney damage, cancers of the lung and bone, respiratory disease, neurocognitive disorders, chromosomal damage and birth defects.

Thirdly, a new war would pose a serious threat to the biodiversity of the region. Data on Iraq's biodiversity is limited. There is little information on fish, amphibians and reptiles. No major surveys have been conducted since 1979. But Iraq's wetlands have been of major international significance, especially for wildfowl. Thirty-three Iraqi wetlands were included on a 1993 provisional list of wetlands of international importance in the Middle East. They supported substantial numbers of at least seven species of mammals and birds listed in the IUCN Red List of Threatened Animals, and were of international importance as a staging and wintering area for more than sixty species of waterfowl and nine species of birds of prey. They were also of great cultural significance, having provided a home for the Ma'dan or Marsh Arabs for at least five thousand years.

Other species would be seriously threatened. According to the Global Environment Fund, the Gulf and Sea of Oman region is "one of the most important marine turtle habitats in the world ... and plays a significant role in sustaining the life cycle of the marine turtle populations in the whole North-Western Indo Pacific region" due to its shallow depth and high water temperature. Of the seven species of marine turtles in the world five are found here. Four are 'endangered' and one 'threatened'.

In the 1991 Gulf War, fallout from burning oil products produced a sea surface microlayer that was toxic to plankton and the larval stages of marine organisms. Sea temperatures also fell. The World Conservation Monitoring Society state that acute effects were experienced by birds and marine life such as otters and dugong. Prawn fisheries were dramatically affected in the years immediately after the war. In 1991-92 spawning biomass in the Saudi Arabian prawn stock dropped to less than tenth of pre-war levels, and total biomass to a quarter. Landings in the Bahraini prawn fisheries dropped by a half.

Of course, it would be absurd to worry about what war could do to animal species without also setting out the worst likely effects of all: the deaths, injuries, loss and grief the war will cause to civilians. The destruction of communities and the displacement of populations are just as much an issue for environmentalists as the damage war does to fragile ecosystems.

Since the Second World War, more than four fifths of the people killed in war have been civilians. Globally there are already 18 million international refugees from war, and another 24 million people are displaced within their own countries. According to the UN Office for the Coordination of Humanitarian Affairs, four fifths of displaced people are women and children. Wars typically cause the break-up of families, the collapse of education systems and consequent widespread social and psychological damage to civilians.

The first Gulf War in 1991, the devastating effect of economic sanctions and Saddam's repression of his own people have already created five million Iraqi refugees and displaced up to one million people inside the country, particularly Kurds and Ma'had Marsh Arabs. Likely civilian casualties in a ground invasion of Iraq have been estimated at between thirty and forty thousand. The most vulnerable communities are likely to be Kurds and Shi'a Moslems.

None of this evidence is certain: but it suggests what the risks of war might be. Nor does it give a conclusive answer to the question of whether war against Iraq can ever be justified. But one of the tests of a just war is whether the likely damage outweighs the possible benefits. And in a democracy we have a right to demand that our leaders consider the possible risks as well as the possible benefits, publish the evidence they have taken into account, and show us why the risks are worth taking.