Environmental Engineering Reference
In-Depth Information
is considerably higher than that of the original grassland (prairie) that covered the
Red River l oodplain before the westward push of European settlers. The result: an
“anthrome” that harbors more phytomass and has a higher NPP than its natural
predecessor.
This example (repeated either in similar or other guises worldwide) raises an
obvious question: why should all ecosystems that have been strongly inl uenced
by human actions be automatically considered inferior, or at least less desirable,
plant assemblages than their natural predecessors? Not only will some disturbed,
regenerated, or planted ecosystems have an NPP rivaling the NPP of their natural
predecessors, they could be nearly as good from the functional heterotrophic per-
spective. For example, Edwards et al. (2010) surveyed 18 sites in Borneo using
birds and dung beetles as indicators of biodiversity and found that 75% of all
species that lived in untouched forests continued to live at twice-logged sites!
And how is selective logging functionally different from damage that is periodically
inl icted on forests by various natural disturbances and disasters? How funda-
mental is the difference between a clear-cut forest and an area whose plant cover
was denuded by a strong hurricane, the latter being a periodic occurrence in eastern
American forests as far north as New England (Foster and Aber 2004)? These
realities make the anthromic/natural dichotomy a matter of choice, and often of
a highly arguable one.
Arbitrary distinctions, dei nitions, and boundaries have been also involved in the
global quantii cations of the remaining “wilderness.” The i rst such inventory dei ned
it as contiguous blocks larger than 400,000 ha: during the late 1980s such blocks
still covered more than a third of the global land surface (nearly 48 Gm
2
), but 40%
of that total was in the Arctic or Antarctic (McCloskey and Spalding 1989). National
shares of the remaining wilderness ranged from 65% for Canada to less than 2%
for Mexico and Nigeria. Sweden (with about 5%) was the only European country
to qualify: no other nations had such large tracts of undisturbed land, nor did such
tropical regions as the Guinean highlands, Madagascar, Java, and Sumatra, or the
rich temperate broadleaf forests of eastern North America, China, or California.
The second study of “the last of the wild” used several criteria to calculate human
inl uence index scores, assigning numbers to all areas with a population density
greater than 1 person/km
2
; agricultural land use; built-up areas and settlements; all
land within 15 km of roads, railways, major rivers, and coastlines; and areas of
nighttime light bright enough to be seen on satellite images. The authors admitted
that they might have overestimated the spatial extent of human inl uence but added
up their numbers anyway to conclude that 83% of the land surface is inl uenced by
