Sir

Current international policy responses to the world's two most serious problems, poverty and climate change, seem to be pulling in opposite directions.

To boost economic growth in less developed countries, international development agencies and the World Trade Organization at the Doha conference in 2001 called for a reduction in European Union and US food subsidies and the removal of trade barriers. This drive towards globalization, resulting in a free flow of trade across borders, should benefit the poorest nations through increased access to global export markets, investment capital and improved technology. These in turn should increase job opportunities and reduce poverty. According to the World Bank's 2003 report, international tourism is expected to play a major role in sustainable development of all the 49 least developed countries, where it currently provides the primary source of foreign exchange earnings.

At the same time, the pressing need to reduce greenhouse-gas emissions is becoming ever clearer. Politicians can no longer evade a range of tough policy choices, as outlined in your Editorial “Light at the end of the tunnel” (Nature 445, 567; 2007).

International scientific and political debates on mitigating climate change through reducing emissions have begun to focus on the transport sector. This accounts for some 20% of global CO2 emissions, a share that is rising rapidly. In response, political pressure by environmental groups and concerned consumers is pushing retailers to reduce 'food miles' — the distance that products travel from field to plate — by sourcing food locally. Tourism is also being targeted by environmental campaigners, as a major contributor to climate change through aircraft emissions. International aviation and shipping are currently excluded from the national emission-control targets set under the Kyoto Protocol. However, it seems increasingly unlikely that such an exclusion from future agreements will be tenable, in the face of strong evidence for the seriousness of potential climate change.

A major disjunction is, therefore, looming between climate policy and strategies for reducing poverty. This illustrates the scale of the tough choices now facing politicians. Attempts to control greenhouse-gas emissions may restrict international trade and tourism, removing the key strategies for less developed countries to grow their way out of poverty. Ironically, the same countries are most vulnerable to the direct impacts of climate change and have the lowest capacity to adapt.

Climate change therefore seems to demand that the international community should find new ways of transferring wealth from rich to poor countries, instead of relying on ever-increasing volumes of trade and tourism with their associated greenhouse-gas emissions.