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Endangering and Protecting Biodiversity

During the course of global history, there has always been turnover of species. This means that species that did not find their niche died out or were eliminated by natural catastrophes. However, evolution and speciation balanced this loss of species. At present, vastly more species are lost than are formed during the same period. According to May (1988), about half of the species developed in the last 50-100 million years will be eradicated in the next 10-50 years, if the current scale of forest destruction in the tropics is maintained. This dramatic relationship be

Fig. 4.2.23. Comparison of two models of the importance of the relationship between species-richness and ecosystem functions. C Species-poor and species-rich communities with relatively stenoecic species which have requirements (and functions) which hardly overlap (A, B) as well as species-poor and species-rich communities with relative euryoecic species which have requirements (and functions) which substantially overlap (D, E). In the two last cases functional redundancy occurs. (After Wright 1989)

tween the rate at which new species form to the rate of species loss is possibly too optimistic according to Nepstadt et al. (1999), as the loss of species in the remaining tropical forests by fires and extensive use is not included in the loss calculations for tropical forests.

There is no linear relationship between number of species and area. Pimm and Raven (2000) predict that with loss of half of all humid forests "only" 15% of species living there would be lost. However, if only 5% of forests remain undisturbed, only half of the forest species will be able to survive. For hot spots of species distribution much higher losses are predicted. However, exact figures are hard to obtain and those available are unreliable. It is impossible to transfer loss of species from one group (e.g. butterflies) to another (e.g. birds) along a linear gradient of exploitation, as the loss in the same area differs considerably for different groups of organisms (Lawton et al. 1998).

At present, direct and indirect human intervention are the most important causes of the increasing loss of species. In the early years of growing environmental consciousness, pollution of the biosphere with pesticides and other toxic

Fig. 4.2.23. Comparison of two models of the importance of the relationship between species-richness and ecosystem functions. C Species-poor and species-rich communities with relatively stenoecic species which have requirements (and functions) which hardly overlap (A, B) as well as species-poor and species-rich communities with relative euryoecic species which have requirements (and functions) which substantially overlap (D, E). In the two last cases functional redundancy occurs. (After Wright 1989)

substances was regarded as the main cause for the loss of species and Rachel Carson (1962) described this impressively in her book The Silent Spring. Today, increasing intensive agriculture and industrialisation are seen as causes. These are linked to fragmentation of the remaining almost natural areas, with drainage, eutrophica-tion, loss of traditional rotation methods in agriculture and grazing, and replacement by monocultures, developments which are described by Krebs et al. (1999) as the "Second Silent Spring". The consequence is not only the direct loss of species, but also the loss of rare habitats. Changes resulting from this global change (see Chap. 5) cannot yet be estimated.

Man is breaking all existing biogeographical barriers. In addition to species extinction, there is a noticeable invasion (neophytisation), particularly a trend to global floristic uniformity with euryoecic species dominating. Lôvei (1997) speaks of a 'MacDonaldisation' of the biosphere.

Maintaining and protecting biological diversity at all organisational levels require no special reasons other than the numerous arguments from ethics, religion, economy and ecology. Because we expect the decrease in species not only to affect the stability and function of our ecosystems, but also to limit future developments, we must apply controls and protective measures. Spatial and environmental planning requires instructions, to protect species, communities and their habitats, which are understandable and can be rapidly and practically applied. Simple biomonitoring, with individual species accurately registered and regularly traced during certain periods in controlled areas, would be a first step in underpinning assumptions and estimates with real data. Reduction in pollution of the environment and attempts to maintain the remnants of natural habitats in all biomes are obviously necessary.

Scientists have developed several instruments for the protection of the environment and some have already been successfully used in practice. It is clear that:

• protection of species alone does not suffice; the habitat and the natural processes occurring there must also be protected;

• increasing fragmentation must be counteracted by integration of habitats (biotope network);

Biodiversity is mainly understood to be the number of species (richness). These developed, via evolutionary processes, over time and with spatial differentiation of specific niches in habitats. In the first inclusive concepts of biodiversity, particular attention was placed on the number of species in a specific area (i.e. plant communities) and between selected areas (within and between habitat diversity; Whittaker 1977). Later, it was shown that diversity could be described in another way. Thus, concepts such as keystone species were used to express the fact that not all species have the same function in an ecosystem. Discussion is now mainly on plant functional types, particularly those that have an important place in ecosystems and their interactions and functions.

Later, it was appreciated that biodiversity is not only the number of species. Of equal importance is the diversity of structures and the functional interactions between them. More importantly the increased numbers of aspects

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