What does this entail? Firstly, it requires that we are able to demonstrate the value of the benefits that society places on biodiversity. Secondly, even if can be shown that--in principle--society does better for itself by protecting biodiversity--in practice--the success of policies to realise this goal may well depend on the capture of these values in order to properly finance increased conservation efforts. In what follows, we expand on each of these points in turn. Protecting biodiversity costs money and so gathering information about the benefits of protection will enable an assessment of whether the benefits of that action exceed its costs.  However, simply stating the broad economic logic is the easy bit--actually demonstrating what these benefits are in a way that is comparable to available information on costs is somewhat more tricky.

What is clear is that these benefits derive from multiple sources. Biodiversity, as represented by myriad types of flora and fauna, provides a storehouse of potential information of future commercial, agricultural or pharmaceutical value. Several studies have tried to estimate the value of a unit of tropical rainforest based on its potential for finding the genetic material for life-saving pharmaceutical products. This is the value of 'bioprospecting'. The potential health benefits of such finds, for example in terms of lives saved, could be very high indeed. However, offsetting this is the observation that the prospects of such a find are generally very small. Thus there seems to be some agreement in the literature that the benefit of bioprospecting is rather low, at least in terms of justifying substantial conservation efforts.

Another way in which the value people place on biodiversity is reflected in the market-place is by the demand for ecotourism, such as safari holidays. In such examples, people pay significant sums for the opportunity to view animals such as lions and elephants in their natural habitats.

However, looking at the money that people actually or might spend on activities related to or dependent on the continued existence of a rich store of diversity only takes us so far in talking about the benefits of biodiversity conservation. For example, what about the majority of people who do not find the prospect of a fortnight under canvas in a tropical forest an enticing holiday opportunity? Is it the case that these people do not care about the continued existence of tropical forests? For many the answer to this question is probably no; the enduring popularity of wildlife documentaries on television is but one example. Indeed, it is plausible that many people value the continued existence of unique ecosystems (such as tropical forests) and animals (such as the African elephant) regardless of whether they ever intend to visit them. Such people are said to hold 'non-use values'.

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A peacock. Kew Gardens is home to many species of bird, including those foreign to the UK.

One US study asked a number of non-users representative of US households how much they were willing to contribute to a global fund that would seek to protect 5 percent of the world's remaining tropical forests. The finding was that each household was, on average, prepared to contribute $21-31. Aggregated across 91 million US households, this amounts to a value of the order of $2.6-2.9 billion as a one-off payment, or roughly $100 million per year on an annuitized basis. This gives at least some indication of the sorts of money that might be raised if such a fund actually existed. It is clearly a substantial sum, although unfortunately not of the order of magnitude said to be needed to deal with the loss of global biodiversity currently being experienced.

A study in the UK looked at willingness to pay for programmes that would extend the survival of black rhino populations in Namibia. Although listed as endangered under the Convention on International Trade in Endangered Species, and having been the subject of extraordinary control measures in many of its range states, black rhino populations in Namibia have fallen dramatically from an estimated 100,000 in 1960 to about 2,500 in 1997. In fact, no country in Africa now carries the minimum viable population of 2,000. Thus in all likelihood the black rhino will become extinct in the near future in the absence of a major upturn in the success of policy measures. Interestingly, this study of what people would pay to extend the survival of the Namibian black rhino population found that, while people were willing to pay some positive amount for preserving rhinos in perpetuity, they were not willing to pay anything at all for an alternative programme that guaranteed that the rhinos survived for 25 years longer than current predictions of extinction. In other words, the rhinos' continued survival only provided value to the extent that it could be sustained into the indefinite future.

It is important to recognise that conserving biodiversity--perhaps by protecting greater and greater amounts of habitat from development--will confer costs on society as well as benefits. Costs arise because, in conserving species by, for example, protecting habitat, society has to close off other options available to it. For example, the decision to designate 10,000 hectares of land as a National Park means preventing the land from being put to some other valuable use. It may be that, in the absence of the Park project, much of this land would have been converted to farmland. If farming is the most valuable alternative use of the land, then the value of the agricultural production that is forgone as a result of establishing a Park is a good measure of the costs of the project. (This is in addition to the costs of setting up and running the Park itself.)

A practical consequence of the setting up of the Park is that farmers who are displaced or otherwise prevented from using the protected land may need to be compensated. This is not just an issue of fairness in that the project imposes a restriction on the ability of people to earn a living from farming in the area. Compensating those who lose as a result of the Park being created is a key element of ensuring the success of the project. In other words, it ensures that nobody is made worse off as a result of the Park. This is one way in which the co-operation of farmers might be secured.

This raises all sorts of interesting questions about how this compensation--and biodiversity conservation in general--can be financed. One way is to seek ways to capture or appropriate the value that people place on conservation. Of course, an immediate problem is that as we have seen--for example, in the case of the Black Rhino--these values are plausibly held by people in countries other than the one where the species resides. Capturing value in this case requires the existence of international institutions to make transfers from those who benefit from the protection of the Rhino (e.g., non-users in the UK) to those who lose from protection (e.g., hunters in Namibia). Such mechanisms, in essence, have been put into effect by the Global Environment Facility (GEF), debt-for-nature swaps by organisations such as the World Wildlife Fund (WWF) and endorsed in international environmental agreements such as the Convention for Biodiversity. However, there is still a long way to go.

Debates about the costs and benefits of biodiversity and habitat conservation can be found closer to home as well. For example, in the United Kingdom there is growing interest in countryside management. That is, there is a whole array of different land-use options lying between leaving nature to itself and intensively farming land or allowing urban development to encroach. Each option will have different implications for habitat and thus the biological diversity of the countryside. Exactly what types of rural landscape the public in the UK would prefer is another matter.