2 Altering the environment
Later in this course we will be considering a number of ways in which humans alter their environment.
In what ways do you think we are altering the environment?
There are numerous possible answers here and the list that follows is not exhaustive. Most people would point to the built environment, the creation of towns and cities and their industrial base, before moving on to the pollution that goes with a modern lifestyle. If you thought about the clearing of tropical rainforests, you might have appreciated that the temperate forests have also largely gone to make way for agricultural land. You might have global warming and the extinction of species down on your list too.
We will be looking at all these ideas, but it is worth pointing out that we are about to consider a number of topics that are very complex and fraught with uncertainties. Even if we devoted more time to them we would still be unable to fully answer the question of what we should do to ensure a healthy planet. It is clear that humans are not unique in affecting their environment. Many large mammals make very noticeable changes to their environment. For example, the passage of a herd of elephants through an area can be as obvious as the visit of a plague of locusts. Not only does their feeding behaviour destroy woodland, but other species are destroyed as they trample around their feeding area. Like hippopotamuses, which enjoy a watery wallow and thereby transform clear pools into areas of ‘mud, glorious mud’ (to quote a well-known song!).
All species alter their environment to some extent, and you may be able to think of examples of this, particularly if you own pets.
Spend a minute or two listing such examples.
Cat owners often notice that there are fewer birds nesting in their gardens than in neighbouring ones, which is just one example of the more general observation that carnivores reduce the numbers of their prey species. The effects of herbivores grazing will be familiar to any gardener with a slug or rabbit problem, as will the beneficial effects of earthworms aerating the soil. Brown patches of dead grass often appear after the ground has been urinated upon by dogs or horses, demonstrating clearly that too much nitrogen has a detrimental effect on vegetation in the short-term. All of these interactions remind us that many organisms share physical space and coexist in a state of dynamic equilibrium. The study of these interactions is the subject matter of the branch of biology known as ecology, but unravelling the extent of the interdependence of organisms is unnecessarily complex for our purposes. However, we will spend a little time gaining some background information so that we can put our own activities into context.