Sir

The recent interest by private-sector institutions in conserving biodiversity is encouraging1,2,3, but in our view government investment remains essential.

In the first place, the private sector is not well equipped to provide public goods related to the global environment. Once provided, public goods are freely available. Ecosystem resilience, aesthetic and existence values, and the option values of biological resources all contain significant public goods related to environmental security4. But the respective roles of public and private sectors in providing biodiversity are not straightforward, because most ecological units generate both public and private goods. Private investment, such as in a nature reserve, often creates public goods, but this cannot always be expected. For example, it may not adequately conserve non-economic (or unappealing) species, nor preserve habitats at the expense of profitable development alternatives.

Also, the rate of biodiversity decline demands action now. Private conservation efforts are far from adequate, especially in developing countries. Delaying widespread action until private-sector investment has greatly expanded would be hazardous.

We think that government intervention to promote biodiversity conservation is essential in three respects. First, governments must provide most of the increased funding needed to conserve a representative sample of the Earth's ecosystems, at least until such requirements can be met by the private sector. We estimate that this might cost around US$27.5 billion annually, compared to the $6 billion currently spent by governments, private sector and foreign donor institutions5. If the international community values the global public goods provided by biodiversity, it must greatly increase its financing of conservation, particularly in developing countries.

Second, private-sector conservation rarely succeeds without government incentives, either in developed6 or developing7 countries. These include expanding legal definitions of property rights to cover environmental resources; reducing costs through help with information technology, administration and enforcement; and providing an effective framework of regulation.

Third, governments must cut environmentally perverse subsidies in natural-resource sectors8. These not only harm biodiversity directly but also inflate the costs of conservation by increasing the profitability of non-sustainable options.

Anyone who doubts that governmental and intergovernmental policy can profoundly alter biodiversity need only examine the impact of schemes such as the EU's Common Agricultural Policy. By subsidizing the over-production of food, this has greatly accelerated agricultural intensification, resulting in the widespread and rapid decline of many birds, insects, plants and traditional farming landscapes9. Reducing such subsidies would save taxpayers' money, free government funds for conservation, and reduce the costs to public and private sectors of expanding efforts to stem the loss of biodiversity.