Chapter IV, Section C, Item 4:  Reduction in Biodiversity

The greatest environmental threat to humanity, in terms of both economic and environmental sustainability, is the reduction of biodiversity. The energy liability from the loss of even a single species can be immeasurable. All other environmental issues, including climate change, loss of habitat from human land uses, and the categories of sustainability outlined in terms of energy liability above – contaminants, acid precipitation, and eutrophication – are problems, ultimately, because they lead to biodiversity loss. Fundamentally, environmental stresses create extreme conditions in ecosystems, conditions that are tolerated by fewer organisms. The life process of each species is part of the entire functioning of an ecosystem, thus in turn, the reduction in biodiversity leads to instability of the ecosystem, potentially leading to ecosystem change or even collapse.

A species in an ecosystem lives within a range of conditions it can tolerate, and its life, the sum of its biological interactions with other species and the environment, effects changes that are part of the functioning of the ecosystem as a whole. Each species thus has a “place” and a “role” that ecologists refer to as a niche, though what constitutes a niche may be measured and defined differently depending on the system being studied. To avoid anthropomorphism, most “roles” are defined relative to the basic functions of an ecosystem: moving energy through the trophic levels and cycling nutrients within the system. Thus species roles are most often related to the biological interactions of feeding and nutrient absorption, the net effect of which is the maintenance of the population balance of species. In this context, however, each species “contributes” to the whole life-supporting ecosystem itself, and thus all species are interconnected. Due to competitive exclusion, most niches can only be occupied by a single species. However there is significant overlap of individual niches. With high biodiversity, most niche roles can be replaced by another species, building redundancy into an ecosystem’s sub-systems. With low biodiversity, the ecosystem is more susceptible to adversity. The extinction of a single species, then, can have disastrous consequences for an ecosystem at large.

Significantly, one of the first post-Earth day pieces of legislation was the Endangered Species Act (ESA), which has been both celebrated for its successes and vilified for its excesses. Originally conceived in the emotional context of species preservation, largely in response to Rachel Carson’s nightmare scenario of bird extinction in Silent Spring, the emphasis has shifted to habitat preservation. The line between habitat preservation and preservationism was, arguably, often crossed. We now come full circle to the central role ESA plays in sustainability. The new view, largely promoted by Al Gore, is that the emphasis of ESA must shift from species preservation to ecosystem preservation, that if you save the ecosystem, you’ll save the endangered species of interest. The top carnivores–wolves, bears, tigers, eagles–are most often the species of preservation interest, and their populations are a measure of ecosystem health. However, those with a financial interest in their prey are less enthusiastic about their preservation.

The term “ecosystem collapse” is popular in the press, though its definition is subjective, depending on the definition of both the ecosystem and the collapse. If the ecosystem is defined only in terms of geography, it can undergo radical change from one ecosystem to another, as in the case of natural eutrophication succeeding a lake ecosystem to that of a swamp. The new ecosystem may be less desirable than the former, and from that perspective, the species of the former have “collapsed” and been replaced by the newer. If we define “collapse” as a reduction in biodiversity, then as an example, the Gulf Coast’s biologically diverse, marine ecosystem that used to support shrimp fishing has very definitely collapsed, at least locally, into a relatively primitive ecosystem of algal blooms and jellyfish. In that case, the economic consequences are readily apparent.

If by “ecosystem” we mean the entire Earth ecosystem, and by “collapse” we mean a major geological extinction event, one including our own extinction, then we are talking about an ecological doomsday scenario. But even this collapse is defined by our perspective. Throughout the history of life on the planet, life has continued on after major extinction events, life with some kind of ecosystem supporting it. The term ecosystem collapse is thus an admonishment to prevent our own collapse, promoting a movement for sustainability, and not necessarily the “save the planet” environmentalism. As George Carlin put it, “The planet is fine...Been here four and a half billion years...The planet will be here for a long, long, LONG time after we're gone.”

Ironically, the threats posed by the loss of biodiversity may have finally entered the consciousness of the public at large by an exemplary economic issue, a major threat to U.S. agriculture: the recent perplexing loss of Western honeybee colonies. Ecologists refer to a keystone species as a species that plays such a critical role in its ecosystem that without it, the ecosystem fundamentally changes. Usually keystone species are predators whose role is to keep another population in check. Other critical roles include nutrient cycling, decomposing, and pollination. The Western honeybee was introduced to North America, replacing many native pollinators, and thus it is not a keystone species to native North American ecosystems. Other insects pollinate; they can and do move into the niche, underscoring the resiliency of a biodiverse ecosystem. But once again, the concern over ecosystem change is from an economic perspective, an agricultural economy of certain crops relying solely on the Western honeybee for pollination. Unfortunately the energy value of biodiversity loss in this case, as in many cases, is immeasurable. The irony is that the immeasurability itself is what leads to its neglect, thus left neglectfully unaccounted in economic terms. The energy value of a single species loss can be as immeasurable as an artificial pollination mechanism is inconceivable.


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