Preserving biodiversity

An extremely difficult, but also very urgent, question we can ask at this point is what humanity should do to preserve the diversity of our biosphere. Obviously, we cannot expect to fully answer the question in a few lines. However, we try to introduce the reader to the problem by summarizing the terms of the most urgent question that arises nowadays: in what direction should we direct our efforts at the global level? As with all the other problems faced by humanity, the financial or other resources that can be devoted to solving the issue are necessarily finite. Therefore, there exists a problem of optimal allocation of money, time, labour and so on. “Where should our money go? Into preserving the Mediterranean flora or the Australian fauna?” As already stated at the beginning of this chapter, Myers et al. (2000) have identified 25 hotspots of biodiversity all over the world using as indicators the species endemism and the level of threat that species are subjected to. The analysis of Myers sparked a useful debate. Obviously, the optimal allocation of resources to conserve biodiversity is a multi-criterial problem: the answer depends on the criterion that is used to define optimality. Recently, Orme et al. (2005) conducted a very interesting analysis on the biodiversity of birds (avian fauna is very well-known) considering three different criteria for each site: species richness, the threat to the species, and the wealth of endemic species. The resulting hotspots are not the same, as the reader can see by examining the three maps in three different colours reported in Fig. 15. However, as noted by Gatto and Casagrandi (2007), there is a certain overlap between the areas identified by using the three different criteria. The wealth of endemic species seems to be the most representative criterion, because it includes areas and species that are also included by the other two criteria. It is remarkable that hotspots of avian fauna are mainly located in highlands and islands.

Figure 15: Hotspots of species richness (in green), hotspots of endangered species (in yellow) and hotspots of endemic species (in red). Modified by Gatto and Casagrandi (2007) after data in Orme et al. (2005)

Figure 16: Map of critically threatened ecoregions worldwide. Reproduced from Hoekstra et al. (2005).

The viewpoint of Myers et al. (2000) and Orme et al. (2005) has been partially contradicted by another analysis that considers a different indicator of ecological diversity. It is true that the species is the key concept of biodiversity and the basic unit of life evolution. However, as we already stated earlier, the functioning of ecosystems in their entirety is another extremely important issue. Even the aim of preserving individual species could be better achieved by aiming at the conservation not of the single species, rather of the overall habitat in which species live. Fig. 16 (which is taken from Hoekstra et al., 2005) reports the map of ecoregions (defined as sets of ecological communities typically associated with specific geographic features) that are subject to global crisis. The map outlines another possible goal of ecology preservation, which is that of conserving habitats and biomes that are rapidly disappearing, such as the Mediterranean vegetation. Interestingly, the Tropical Andes (one of the hotspots of Myers) are no longer present in the map of Hoekstra et al. (2005). In fact, they have a very high richness of endemic species, but their habitat is not critically threatened as of now. On the other hand, we must consider that ecosystems that are home to low biodiversity such as, for example, vast tracts of boreal forest that stretch from Russia to Canada, provide important ecological services, for example the absorption of carbon from the atmosphere, which is crucial for mitigating global warming. These ecosystems were not classified by Myers and colleagues as hotspots of biodiversity, yet they are definitely worth being preserved. We can therefore say that the debate is still very open.

A very important issue for the conservation of global biodiversity is also that of gap species. During the 5th World Parks Congress, Durban, South Africa, in September 2003, it was officially announced that the global network of protected areas covered at least formally, 11.5 % of the land of our planet. This seemed to be a good result, even beyond the objectives set ten years earlier. However, protected areas are not designed in a way to really preserve a considerable amount of biodiversity. In particular, there are many species that have been officially declared endangered by IUCN and whose current range is not within any protected area (Rodrigues et al., 2004). These species have been named gap species. Overall, 20% of the endangered species that were analyzed were identified as gap species. In particular, among them there are many amphibians. It is therefore urgent to extend the network of protected areas in such a way that they host the greatest number of endangered or critically endangered species.

For more information on the currently most debated topics please refer to the 4th edition of Global Biodiversity Outlook (that can be freely downloaded at http://www.cbd.int/gbo4).