On many left lists, in the West in particular, if you talk about the unsustainability of current human population and consumption, you are often labelled a "neo-Malthusean" and further, an enemy of the common folks and an advocate of population control of the worst kind. A popular modern version of this debate is the Simon-Ehrlich wager, between conservative economist Simon and eco-activistic (and in that sense leftist) biologist Ehrlich; the twist being that it is the conservative who argues against any dangers posed by human population. For the record, Ehrlich lost that wager handily.
Ehrlich offered a newer list of criteria that Simon found unnacceptable (see link above). What is interesting about the new list is that Ehrlich finally starts thinking outside the [human] consumption trap (and the rephrasing of the issue as one of the effects of human consumption).
Recently, biologist Eric Pianka, at the University of Texas, has been in hot water over his own doomsday predictions about disease and death among human populations. I do not know the background of this guy and his affiliations. However, the following note from his website is an excellent argument of why human arrogance and ignorance, in this context, are morally repugnant.
What nobody wants to hear, but everyone needs to know
Eric R. Pianka
I have two grandchildren and I want them to inherit a stable Earth. But I fear for them. Humans have overpopulated the Earth and in the process have created an ideal nutritional substrate on which bacteria and viruses (microbes) will grow and prosper. We are behaving like bacteria growing on an agar plate, flourishing until natural limits are reached or until another microbe colonizes and takes over, using them as their resource. In addition to our extremely high population density, we are social and mobile, exactly the conditions that favor growth and spread of pathogenic (disease-causing) microbes. I believe it is only a matter of time until microbes once again assert control over our population, since we are unwilling to control it ourselves. This idea has been espoused by ecologists for at least four decades and is nothing new. People just don't want to hear it.
Population crashes caused by disease have happened many times in the past. In the 1330s bubonic plague killed one third of the people in Europe's crowded cities. Smallpox and measles decimated Native Americans when Europeans transported them to the new world. HIV is a relatively new disease wreaking havoc in Africa and Asia. Another population crash is inevitable, but the next one will probably be world-wide.
People think unrealistically because they have lost touch with the natural world. Many people today do not really know where and how our food is produced, and on what our life support systems are based. As we continue paving over natural habitats, many think that we can disrupt and despoil the environment indefinitely. We have already taken half of this planet's land surface. Per capita shares of all the things that really matter (air, food, soil, and water) are continuously falling. Our economic system is based on the principle of a chain letter: growth, growth, and more growth. Such runaway growth only expands a bubble that cannot be sustained in a finite world. We are running out of virtually everything from oil, food and land to clean air and water.
Some politicians, economists, and corporations want us to believe that technology will come to our rescue. But we have a false sense of security if we think that science can respond quickly enough to minimize threats from emerging diseases. Microbes have such short lifecycles that they can evolve exceedingly fast, much faster than we can respond to them. Many bacteria have evolved resistance to most antibiotics, and viruses are resistant to just about anything. Defense always lags behind offense. So far, modern humans have just been lucky. A reactive approach to problems isn't enough, we also need to be proactive and anticipate problems before they become too severe to keep them from getting out of control.Many people believe that Earth and all its resources exist solely for human benefit and consumption, this is anthropocentrism. We should allow the millions of other denizens of this Earth some space to live — they evolved here just as we did and have a right to this planet, too.
I do not bear any ill will toward humanity. However, I am convinced that the world WOULD clearly be much better off without so many of us. Simply stopping the destruction of rainforests would help mediate some current planetary ills, including the release of previously unknown pathogens. The ancient Chinese curse "may you live in interesting times" comes to mind — we are living in one of the most interesting times humans have ever experienced. For example, consider the manifold effects of global warming. We need to make a transition to a sustainable world. If we don't, nature is going to do it for us in ways of her own choosing. By definition, these ways will not be ours and they won't be much fun. Think about that.
While he may be temporarily (or even entirely) wrong on the predictions about disease, he is (IMHO) absolutely right on human crowding out of other species, human faith on technology, and in particular our attitude towards the world and how we "consume" it. It is fashionable today (within the left) to dismiss this sort of thing as "new age" sentimentality or "primitivism". The argument deserves more respect.