Johannesburg — MORE than any other continent, Africa is blessed with abundant natural water resources. It is home to the world's longest river, large fresh-water lakes and countless rivers, tributaries and streams.

But our unique natural inheritance is under threat. Across Africa, one can see threats to water supplies and cases of severe environmental degradation.

Most alarmingly, these changes are taking place before the full effect of climate change is being felt. Despite being the least responsible for causing it, Africans now are on the front line of climate change, with sub-Saharan Africa being more vulnerable than any other region in the world. As president of Mozambique, I witnessed first-hand the devastating effect of severe flooding in 2000 and 2001 . Tragically this is unlikely to be the last occurrence of flooding in Africa. A recent report launched by Kofi Annan shows that there is a significantly increased risk of natural disasters due to climate change.

For African policy makers, the environment must now be at the top of the policy agenda, with water sustainability being accorded the highest priority . A number of countries are toughening environmental protections and developing adaptation programmes, but more needs to be done. As African leaders prepare for the Copenhagen summit later this year, there is a new urgency for all countries to develop effective environmental policies at home and to secure a fair and ambitious climate change deal abroad.

It is all the more important when considering the imperative for Africa to sharply and sustainably increase its agricultural productivity. No country in the world has managed to develop its economy and increase standards of living for its people without first significantly increasing agricultural productivity. About 80% of Africans depend on agriculture in one way or another for their livelihood. Yet Africa's yield per hectare for food crops is less than half that of developing countries, less than 10% of its arable land is irrigated, and fertiliser remains scarce.

For African governments, this means not only putting in place the right environmental policies, but also putting money behind the rhetoric of creating a green revolution in Africa. So far, only eight countries have met the Maputo target of allocating 10% of public expenditure to agricultural and rural sectors. At the same time, governments should work to harness the support of the international community.

Above all, African policy makers must embrace technology and develop their own technological solutions. African research institutions are pioneering new forms of irrigation that could transform the way staple foods are cultivated, fertilisers are available that can feed nutrient deficient soils, modern crop varieties can dramatically increase yields and new techniques can make farming significantly more efficient.

It is why, despite all the obstacles we face, I remain such an optimist when it comes to Africa's agricultural development. Our continent has 12 times the land area of India, with only half the population to feed. With few exceptions, the distribution of cultivable land in sub-Saharan Africa is equitable compared to many other regions of the world. Moreover, the technology already exists, demonstrated through the success of improved varieties of cassava, rice and maize. I believe that with the right commitment, policies and technologies, Africa will better the Asian agricultural miracle of the 1970s and 1980s -- in an environmentally sustainable way.

This week, the Pan-Africa Chemistry Network is convening a conference to assess the challenge of water sustainability. It will bring together scientists from across Africa to look at issues of water sustainability and what can be done to secure and harness water supplies. The conference will produce a report for World Water Day next year, outlining a programme for action. I do not doubt that we face unprecedented challenges, but we have the 21st-century expertise with which to overcome them, and the African talent with which to apply them.

Chissano is a former president of Mozambique and is chairman of the Forum of Former African Heads of State and Government.