Changes in Biodiversity: Birds and Mammals and their Use

Abstract

In this chapter a number of birds and mammals will be discussed that have an ecological connection with river habitats, mainly to demonstrate the subjective way of treating these animals as ‘harmful’ or ‘useful’ in the course of the history of the Delta. Notwithstanding the focus on wetland species, the choice remains arbitrary, mainly based on public interest and the ‘cuddliness’ of specific species. In the past mammals were exposed to the same fate as birds. ‘Useful’ species, either big game or small game, were hunted after and poached, and prepared for human consumption and many other applications. ‘Harmful’ species, like wolf and brown bear, were prematurely annihilated, because of their threat for humans, cattle and game. Some other species, like the harbour seal and the otter, were considered as a severe threat to fisheries, and fell victim to bounty hunters. Just like birds, since a few decades almost all mammal species have a legally protected status, and their population size is artificially controlled. Some species, on the contrary, are rigorously chased because of their assumed harmful habits. What birds and mammals have in common are the large quantitative changes in population size in a given space of time, the past two centuries. Extremes in weather conditions, habitat loss, changes in agricultural practice, environmental pollution and eutrophication, increased pressure of humans on remote and rural areas, and many other factors have been responsible for these fluctuations. Many of these relations will be discussed in this chapter.