Sir

Public funds should not just be channelled into boosting immediate economic recovery — we must also be prepared to pay a higher 'insurance bill' to safeguard the ecological long-term basis of our economic and social well-being. Increased spending on conservation could help fund a worldwide core network of protected areas of biodiversity.

At the beginning of this year, worldwide economic stimulus plans totalled US$2.8 trillion, with some 15.6% allocated to 'green' purposes such as climate protection (http://tinyurl.com/ddrj69). In April, the G20 group of nations announced plans to spend US$5 trillion by the end of 2010, to stimulate the floundering global economy and “accelerate the transition to a green economy”. None of these funds is designated to the conservation of biological diversity — a fundamental resource for our economy and society.

The multilateral Global Environmental Facility (an independent financial organization uniting 178 member governments, in partnership with international institutions, non-governmental organizations and the private sector) has spent US$7.6 billion on biodiversity conservation since 1991. In addition, we estimate that some $7.6 billion has been contributed to this purpose each year by national governments.

We estimate that US$53 billion is needed annually to maintain a global core network of protected areas (our update of figures from A. Balmford et al. Science 297, 950–953; 2002). This amount includes the income opportunities lost for the rural population of poor countries: mainly income that is, or could be, generated from tropical and subtropical agriculture.

It has been known for some time that the public in wealthy countries would be prepared to contribute additional funding to promote biodiversity conservation in the tropics (see, for example, B. Horton et al. Environ. Conserv. 30, 139–146; 2003). We believe that these contributions would today amount to US$42–140 per household per year. Extrapolating this to each of about 452 million households of the member countries of the Organisation for Economic Co-operation and Development, we believe that roughly US$43 billion could be generated annually. This sum would cover most of the global core network of sites earmarked for protection.

A dramatic increase in conservation spending is no fast fix for the economy. But conserving biological diversity contributes crucially to maintaining the resilience and adaptive capacity of the biosphere. In addition, it directly provides a multitude of critical ecological services (see, for example, http://tinyurl.com/oee799).