TABLE OF CONTENTS
THE IMPORTANCE OF BIODIVERSITY TO CANADA
A CONSTANTLY CHANGING ENVIRONMENT
STRATEGIES FOR BIODIVERSITY CONSERVATION
WHAT DO WE MEAN BY BIODIVERSITY?
HUMAN IMPACTS ON BIODIVERSITY
What succession tells us is that there is no natural level of biodiversity. But if Nature is constantly changing, and if extinction is perfectly natural, how can we put parameters on the issue of biodiversity conservation and identify where our intervention is required or how we are doing? Debates over biodiversity tend to focus on what has been lost or on the extent of changes brought about by humans. However, can we, or should we, try to turn back the clock and attempt to recreate conditions that existed fifty, five hundred or five thousand years ago?
In most cases, we are unable to put things back the way we found them (or pretend we aren't here) and instead we must look ahead to decide the type of world we want to live in. In order to do that, we need to examine and understand the types of changes that are occurring in the natural world and the rates at which they are taking place. Whenever conditions are changing faster than species or ecosystems can adapt particularly if humans are contributing to the change or impeding adaptation we need to pay particular attention.
Unexpected changes in biodiversity can forewarn us of changing environmental conditions. The disappearance of a species may be an indication of increased levels of pollution, for example. It may also be an early sign of changing climatic conditions. Many scientists believe that the earth's climate is warming faster than most species and ecosystems can adapt. Islands of habitat that are hemmed in by water, geological obstacles or human development are particularly vulnerable, as there is no place for the affected species to go. In the latter case, humans are contributing to the process of change by releasing greenhouse gases into the atmosphere while at the same time impeding the ability of some species and ecosystems to adapt by cutting off their migratory paths.
Humans can also shorten the process of succession. Commercial forest management fells forests perhaps decades before the natural mortality age of the trees. We also attempt to suppress the natural processes of fire, insects and disease. Logged sites are usually prepared for regeneration which may be helped along by seeding or planting desired tree species. Those trees will generally be scheduled for cutting once they reach maturity. Thus, both the early and late stages of succession may be shortened or lost as forests are brought under management, reducing or eliminating the habitat of those species that depend on these stages in the natural cycles of forests. While these forests may continue to produce timber, other ecological, economic and social benefits may be lost or compromised in the process.
Overexploitation of individual species, such as northern cod and chinook salmon, especially when combined with natural factors such as fluctuating water temperature or human-induced conditions such as the destruction of spawning grounds, can also result in a loss of biodiversity. Individuals are removed from a population faster than their reproductive biology can replace them. The removal of predators from certain areas can also have negative impacts. The overbrowsing of vegetation by high numbers of whitetail deer is one of the major threats to endangered species in southwestern Ontario, for example. And Canadian ecosystems are now home to dozens of introduced species that have become entrenched in our natural environment, occasionally at the expense of those native species that are not adapted to compete with the new arrivals.
All of the above represent human induced changes to the environment which contribute to a loss of biodiversity and have both social and economic, as well as environmental, consequences. To be effective in conserving biodiversity, we need to identify those areas in which our activities are compromising the ability of species and ecosystems to survive and evolve, and develop creative and proactive strategies to address these issues. As change in the natural world is constant, there will never be a specific point at which we will be able to say that we have achieved biodiversity conservation. We can only develop a wide range of targets and indicators to monitor our progress.