The value of biodiversity

A question that is often asked concerns the reasons why we should preserve biodiversity: Is it really so valuable? Isn't it perhaps a waste of money, a luxury that only the affluent countries can afford? Of course, answering this kind of questions requires not only scientific expertise, but also socio-economic and even ethical considerations. The social sciences distinguish between direct value (what we can get directly from organisms, that is food, fiber, timber, etc.), indirect value (related to the services that ecosystems render to humanity for free) and intrinsic value (aesthetic, spiritual, etc.).

While the direct value of biodiversity needs no special comments, it is good to consider indirect value in more depth. We begin by giving a very clear example of the value of ecosystem services. During the tsunami that struck East Asia in December 2004, the areas of Sri Lanka where the coral reef was still intact were invaded by the huge wave only 50 meters from the shoreline and no death was recorded. Unfortunately, this did not happen a few kilometres away where the reefs had been illegally destroyed (Fernando et al., 2005). Here the dead were counted in hundreds.

The services provided by ecosystems are innumerable. The following list of benefits is certainly incomplete, but can serve as a guide for further consideration:

• ecosystems moderate extreme weather events, thus contributing to climate stability;
• mitigate the impacts of floods and droughts;
• protect waterways and coastlines from erosion;
• protect people from harmful ultraviolet rays;
• recycle nutrient salts;
• purify the air and water;
• decompose and purify wastes;
• control agricultural pests;
• regulate organisms that are vectors of infectious diseases;
• disperse seeds and pollinate agricultural and natural vegetation;
• generate and preserve soils and regenerate their fertility.

While in the early 1970s there was a growing awareness that environmental assessment was as necessary as economic evaluation (just think of the legislation on EIA, the Environmental Impact Assessment, which was introduced in North America and Europe), in more recent times the old logic that economic evaluation should prevail over all other considerations gained new force. This new context led Robert Costanza et al. (1997) to conduct a purely monetary, comprehensive evaluation study on the resources and services that biodiversity provides us with. The authors estimated that these services were worth 33 trillion dollars (to provide the reader with an idea of this enormous sum of money, consider that the whole earth's GDP, gross domestic product, was then worth 18 trillion dollars). Although this approach was criticized (see for example Gatto and De Leo, 2000), one must admit that these results should convince even the most sceptical economist on the importance of preserving biodiversity. In other words, Costanza et al. (1997) showed that conserving biodiversity is paid back, because ecosystem services are worth at least twice the global GDP. It should be emphasized that any time we lose a species we might have lost forever, for example, the possibility of treating one of the diseases that ravage humanity. In fact 80% of the human population relies for its treatment on natural medicinal products. Of the 150 drugs most prescribed in the United States, 118 are derived from natural organisms: 74% from plants, 18% from mushrooms, 5% from bacteria and 3% from a vertebrate (snake). Nine of the 10 most used drugs are derived from natural plant products. More than 100,000 different species of animals, including bats, bees, flies, butterflies and birds, freely provide their services as pollinators. A third of the food consumed by humans comes from naturally pollinated plants. The value of natural pollination services in the US alone was estimated to be 4 to 6 billion a year. Several cost-benefit analyses were conducted regarding the services of ecosystems and all of them showed that it is not true that biodiversity conservation is too expensive for the developing world countries. Actually, preservation costs are largely offset by benefits (Balmford et al., 2003; Balmford et al., 2002).