The threat to biodiversity occurs when these dynamics are disturbed beyond the point of recovery. There are two main ways in which this can occur. First, there may be a change in management practices in an area where there has been no change in the actual land use. 'Management' here means the whole range of human involvement in an area. This could be rubber tapping in the Brazilian rainforest, intensive agro-industry in the European countryside, nomadic hunting in Africa or provision for leisure activities in the North American National Parks. All these anthropocentric engagements with nature to some extent involve exploitation of existing ecosystems. In many cases, existing ecosystems will have already changed over time in response to past human involvement, and that can continue in cases where human involvement does not exceed the capacity of the area to cope. However, in some cases the changed management practice--increased numbers of leisure visitors or larger amounts of killed game, the use of new pesticides or mechanised harvesting, or most controversially the introduction of genetically modified organisms into conventional agriculture--can push the ecosystem beyond its threshold and tip it into degradation.

	Thinking Points
	How important do you think habitat biodiversity is for the preservation of species? Do you think the threat to habitats receives enough attention and coverage?

To assess this, we need to understand the impact of old and new management practices on ecosystems. One fertile field for current research lies in the attempt to understand traditional patterns of ecosystem management that appear to have already been sustainable over time. Knowledge of these traditional practices is often termed 'indigenous' or 'lay knowledge'. Of course not all traditional practices are sustainable; some have led to massive losses of biodiversity in the past. But where such practices do appear to have been beneficial, understanding them can be an invaluable adjunct to contemporary scientific knowledge of the impact of fertilisers, pesticides and new genetically engineered species.

The second threat comes with changes in land use itself: the clear felling of the rainforest, the urban development of the countryside, the shift from transitory to more permanent settlement, the introduction of primary industries (such as mining) into previously unexploited areas. Here there is the substitution of one set of relationships between humanity and nature for another. How this affects biodiversity depends on the ecological richness of the original land use compared with the new use. Not all development of itself destroys biodiversity, even where it threatens valued features of the environment. Logging trees in the ecologically unique rainforests is a biodiversity disaster. However, it may be the case that building housing on a greenfield site has little significant impact on biodiversity levels, even if it affects the landscape and other benefits derived from the agrarian countryside.

LSE

Camley Street nature reserve, two acres of wild green space on the banks of the Regents canal in the heart of London. The reserve, just yards away from Kings Cross train station, is a place for both people and wildlife. Special features include a pond, meadow and woodland, providing a natural environment for birds, bees, butterflies, amphibians and a rich variety of plantlife.

For these reasons, it is important to be able to gauge the existing biodiversity value of sites that are likely to be developed and undergo significant change of land use. The designation of sites of special significance under various headings makes a contribution here. Surveys of species diversity across local areas can also be helpful. These kinds of designation and information can feed into regulatory processes that seek to control development and land-use change. Many governments, research institutes and non-governmental organisations (NGOs) are, therefore, investing considerable resources in expanding the knowledge base of biodiversity in their area of influence.

	Thinking Point
	Can you think of examples where ecosystems have been irrevocably altered through human intervention?

But it is important that this expansion of knowledge goes along with the expansion of institutional capacity to actually protect identified areas. This means not only that the information has to be available but also that procedures have to be in place for incorporating that information into regulatory decisions. Only then can the regulatory system deliver decision-making that prioritises the protection of areas of ecological richness and of those management practices that can maintain rather than degrade such areas. Even then, political pressures and bureaucratic inertia may prevent assessment of ecological significance affecting development decisions. Then the hope of protecting biodiversity lies with generating sufficient political counter-pressure to influence the regulatory system. But the prerequisite for both political action and regulatory decisions to protect biodiversity remains an adequate knowledge base. Without such information, the possibilities of land-use change undermining biodiversity are always considerably higher.