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.