Our Dying Planet: An Ecologist's View of the Crisis We Face / Peter F. Sale -- Berkeley, Cal.: University of California Press, 2011

When one reads the title of Peter Sale's book -- Our Dying Planet -- one immediately thinks of the paramount environmental problem of the day: global warming, but the subject is much broader than this. Sale admirably connects a host of environmental problems to provide a stark picture of the planet's peril. The title is, in all likelihood, an overstatement. Our Declining Planet might be a better title, but given the gravity of our situation, Sale's hyperbole is excusable.

Sale is first of all a marine biologist, specializing in coral reefs. So global warming certainly plays an important part in his analysis of our environmental plight; but more than anything, Sale emphasizes the striking loss of biodiversity that is being caused by more than just climate change. His first chapter is an account of the collapse of fisheries, due mainly to overfishing. Much of this is rather well known, but the extent of the collapse would, perhaps, surprise many. Industrial fishing techniques used in the Northwest Atlantic have decimated the cod population there. In 1968, 1.9 million metric tons of cod were caught, but just 22 years later, in 1990, only 80,000 metric tons of cod were caught. This led the Canadian government to close the northern cod fishery in 1992.

One might expect that with a ban on fishing, the cod population would recover, but it has not. This is perhaps the most sobering message that Sale delivers. During the first 100 years of research into ecosystems, the paradigm of a "balance of nature" was dominant. Populations were seen to be regulated naturally by homeostatic mechanisms. When a population declined, its predators declined and its food sources thrived, creating the conditions for recovery; however, by the later half of the twentieth century, ecologists began to recognize the "patchiness" of nature. Species inhabit a constantly changing patchwork of habitats that are tenuously connected to create metapopulations. Inside these patches, the success of individual organisms in surviving and reproducing is more significant than was previously appreciated. The result is that populations are not "resilient" due to homeostatic mechanisms, but instead, exhibit a kind of "inertia." Large populations will continue until a powerful external force depletes them and once depleted, they will tend to remain in their depleted state. The consequence of this dynamic is that the numerous assaults that we have committed against populations are causing damages that are not repairing themselves, leading to an unprecedented rate of species extinctions. The North Atlantic cod, while not extinct, is but one of many examples of the loss of biodiversity that is occurring around the planet; hence, the "dying planet."

As dire as our circumstances are, Sale provides a few chapters that hold out hope or at least suggest ways to confront the problem. The two primary responses he recommends are to reduce our use of fossil fuels and to slow the growth of the human population. Though his chapter on slowing the growth of the human population is brief, it is clearly his most important concern. Sale writes, "Unchecked population growth presents substantial (I am tempted to say insurmountable) impediments to our need to achieve sustainable use of the earth's goods and services. If those of us who understand this do not speak up concerning our population problem, who else will? I fear we have been complacent for far too long." Given that we are already pressing up against the limits of the world's resources, it is hard to believe that we will be able to support the 9.2 billion people expected to be inhabiting the planet by 2050 and so, it is hard to disagree with Sale.

At a time when climate change is the focus of so much attention, it is useful to look at other ecological problems that we face, though certainly a changing climate will exacerbate whatever harms we are doing to the world's biodiversity. The obvious conclusion is that all of these concerns are interrelated and that we must address them all at once. There is no single policy or approach that will mitigate the coming disasters.