If you want to read an article that simultaneously enlights, delights and gives hope, you could do much worse than to read this excellent Aeon essay on extinctions penned by one of the titans of the environmental movement – Stewart Brand.
Brand provides a fascinating counterargument to oft-heard discourse about species extinctions and the “Sixth Mass Extinction” now caused by humans. He argues that biodiversity is in fact increasing dramatically, and has been doing so for the last 200 million years (see the chart below). Despite the sometimes horrendous damage humans can inflict upon the environment and the undeniable plight of many species, we are not destroying the environment as a whole. Instead, “the frightening extinction statistics that we hear” are largely about small island ecosystems that comprise only 3 percent of the Earth’s surface, but are the site of 95% of all bird, 90% of all reptile, and 60% of all mammal extinctions since 1600. (The island ecosystems have not, by and large, collapsed as a result – they’ve evolved to a different form.) Besides, these extinctions have already happened, since most vulnerable species are already gone.
Regrettable as they are, these local losses have very little effect on the overall ecological health of the planet. Brand argues that since continents and oceans are much larger, it is unlikely even major die-offs or habitat destructions would collapse the ecosystems there. Species can move to new locations, and if a species dies, it leaves a niche free for some other species to exploit – and there is some evidence that die-offs are actually accelerating the global evolutionary rates. Islands have been a special case because of their simpler ecosystems, which is also a major reason why they’re also the best studied: they’ve been used as laboratories.
However, the fly in this ointment might be that all we have left may be islands. This was the opinion of a Finnish academician and conservation biologist Ilkka Hanski, who devoted his distinguished career to the study of threatened animal and plant species. Based on his experience on habitat patchiness, developed in part on innumerable small islands in the Finnish archipelago, he developed a theory of “island ecology” on mainlands. (More accurately, “metapopulation theory for fragmented landscapes” – PDF link.) Even though continents are indubitably larger, human activity has in effect made the remaining habitats as islands: small patches of nature amidst a sea of paved roads, power lines, cities, farms, mines, factories and wastelands.
Hanski, whose untimely death in May will be sorely regretted, repeatedly stressed how even seemingly healthy populations that on paper have enough square kilometers to roam may in fact teeter precariously on brink of extinction because their habitats have been fragmented through human activity. This is a major issue that isn’t adequately addressed in many simpler measures of environmental health, and which may well resist quantification into a simple metric.
Nevertheless, habitat fragmentation is a real problem, and while there are some ways to mitigate it (for example, roads may be built with tunnels or bridges that let animals across), it seems clear we simply cannot continue our encroachment into natural spaces without a risk of causing major damage even to continental ecosystems. The nature of this beast is that impacts are nonlinear: habitat fragmentation may go on for quite a while without many noticeable ill effects, but after some threshold is reached, a cascading collapse might well result. Worse, habitat fragmentation also hinders the mechanisms Brand hopes will help restore ecosystems after collapse of keystone species. Species may migrate and there may be a species capable of filling the hole, but what if they can’t move because their remaining habitats are isolated islands in the human-built world?
I cannot claim to know biology in more than the most rudimentary fashion, but Hanski’s writings have impacted me at least quite a bit. Fears of habitat fragmentation are one of the reasons I disagree with traditional environmentalists, as their energy scenarios seem to pay lip service at most to this problem. While all environmental organizations agree that ecosystem degradation is a major problem, they nevertheless see no problems announcing or supporting grand plans that would harness vast areas of the world solely for energy production. As this image shows, such plans are likely to result to significant added habitat fragmentation, even considering that some buildup can be done on areas already disturbed by human activities.
Some may think bringing up energy in a discussion about ecosystem damage is tedious, but I disagree. These things really are interconnected, and it is very hard to conserve and protect Earthly life if, at the same time, we must gird the Earth with the harness of power grids, power farms, and energy plantations.