A global network of nature reserves costing $45bn (€46.4bn,
£28.6bn) a year would produce goods and services worth
more than $4,400bn annually - a benefit-to-cost ratio
of 100-1 - an international team of economists and environmentalists
The study, published in Science magazine, concentrated
on five case studies of wild eco-systems being converted
to human use.
Ecologist Andrew Balmford of Cambridge University said:
"The economics are absolutely stark. We thought the number
would favour conservation, but not by this much."
The study, claimed to be far more comprehensive than
similar work produced by the World Bank and other bodies,
was published ahead of the United Nations summit on sustainable
development, which begins in Johannesburg later this month.
Biodiversity preservation will be considered at the summit,
but it is widely expected little real progress will be
made on implementing measures to protect nature, notably
the Convention of Biological Diversity.
The eco-systems studied included a Malaysian tropical
forest converted to logging, a forest in Cameroon used
for agriculture and commercial plantations, mangrove swamps
in Thailand used for shrimp fishing, a Philippine coral
reef dynamited for fishing and a Canadian marsh drained
In each case the loss of natural services such as storm
and flood protection, carbon sinks and sustainable tourism
outweighed the benefits of conversion for short-term gain.
The economists said pricing such natural services was
difficult without an established market. However, estimates
were made of the cost of replacing the services and assessments
made about how much individuals and nations would be prepared
to pay for relying on naturally provided services.
Robert Constanza, an economist at the University of Maryland
in the US, said a conservative approach had been taken
in valuing such services, yet this still resulted in the
100-1 benefit-cost ratio. Benefits that had proved difficult
to value had not been included but would increase the
ratio further, he said.
Paul Jefferiss, head of environmental policy at the Royal
Society for the Protection of Birds, the UK environmental
group which co-ordinated the study with Cambridge University,
said the study demonstrated the need for changed thinking
by the World Bank and others.