The United Nations Environmental Programme (UNEP) will be looking for a new director-general at the end of this year, and the UN World Summit this week may consider steps to widen the body's influence.

UNEP's departing director, former German environment minister Klaus Töpfer, has worked hard during his eight years in office to strengthen the body's ties with industry, and to get its work taken seriously beyond the narrow circle of environmental groups that have supported its efforts in the past.

But a great deal more needs to be done if this relatively obscure office, with about 450 professional staff and an annual budget of US$60 million, is to make any real impact on epic global environmental problems such as global warming, clean air, clean water and biodiversity conservation.

UNEP was set up in 1972 with a mission “to provide leadership and encourage partnership in caring for the environment by inspiring, informing, and enabling nations and peoples to improve their quality of life without compromising that of future generations”.

The programme has scored some notable successes on Töpfer's watch, helping to coordinate international discussions on water-supply issues, for example, and helping poor countries develop laws and regulations on complex issues such as the transportation of biological specimens and transgenic plants.

But UNEP is not currently constituted to provide genuine leadership on critical environmental issues, even when these cry out for an international response. Unlike fully fledged UN agencies such as the Food and Agriculture Organization or the World Health Organization, it is merely a ‘programme’, funded on a voluntary basis by the United Nations' member states.

Perhaps the outfit whose clout contrasts most vividly with UNEP's is the World Trade Organization, which is independent of the United Nations and arbitrates forcefully and effectively in disputes between its member states. UNEP, on the other hand, has neither ways to settle disputes nor mechanisms to enforce compliance with international environmental agreements such as the Convention on Biological Diversity.

UNEP's problem is that it lacks the power to enforce the growing number of binding environmental deals between nations.

UNEP's remit is more modest than that. Its job is to set and monitor standards for environmental protection and sustainable development around the world, in collaboration with local governments, scientists, non-governmental organizations and other interested parties. This responsibility stretches from biodiversity to climate change, from managing clean water to desertification, and from bio-safety to problems posed by invasive species.

Under Töpfer, UNEP has improved its use of scientific information, and gained better access to the corridors of corporate power. On the downside, Töpfer has been drawn into distracting public disputes with other international bodies, over issues such as the administration of the Global Environment Facility, which finances environmental projects (see Nature 394, 4; 199810.1038/27719).

But UNEP's real problem is that it lacks the power to enforce the growing number of binding environmental agreements between nations. Beefing up the programme would probably involve a mandatory funding scheme based on the size of members' economies. Plans for this have been around for years, but they face significant obstacles, starting with the opposition of the United States, which currently contributes less than either the United Kingdom or Germany to UNEP's budget.

Such funding concerns hide a broader fear, by no means confined to the United States, that a more powerful UNEP would constrain the freedom that national governments currently enjoy to pollute pretty much as they please. This may be short-sighted, however. In the long run, national governments — and global capitalism, for that matter — might benefit from a strong international environmental body, a World Environmental Organization, if you will, with a remit to safeguard the future of the planet.

Töpfer has helped UNEP to build bridges with the worlds of business and finance, and sought to convince business leaders that sustainable development and a healthy environment are in their interest, too.

The UN Summit could strengthen UNEP in the short term by merging it with the smaller, separate UN Division for Sustainable Development, currently a branch of the UN Department of Economic and Social Affairs. Secretary-General Kofi Annan then needs to appoint a heavyweight successor to Töpfer who can provide UNEP with energetic and determined leadership. That person should continue the policy of partnership with industry, while carefully guarding the organization's independence and further nurturing its credibility, in preparation for the day when national governments are ready to upgrade its status.