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HISTORICAL-ERA EXTINCTIONS

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We run into a problem with what constitutes "historical era".  Arbitrarily, I present this as since the advent of "modern" technology, or basically since about 1500 AD.  There are, however, a few instances of earlier extinctions preceding this date that I include and still attribute to human capability (especially in landscape modification).

More importantly, escalating human populations and their capacity to modify their surroundings are a significant influence on modern rates of extinction and endangerment.   As examples I focus here on the "cute and cuddlies", particularly maps of birds and mammals, because they are noticeable, imaginable, and therefore better documented than other organisms.  However, other classes of organisms face similar levels of threat, regardless of our emotional affinity towards them.

It is no mere coincidence that as human populations (and technological prowess) have risen, so too has the incidence of extinction.  The long-term geologic record suggests that on average there should be about six to eight mammal and bird species that disappear each century, but the graph below clearly suggests that excessive losses parallel the advent of modern technology and transportation, and growing numbers of humans using these.  Barring significant adjustment of human interaction with critical habitats, it seems likely that this escalation of extinction rates will continue.   

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The examples and inventories are symptomatic, but not inclusive.  My primary interest is to examine spatial patterns of loss, not resolve taxonomic arguments.  The latter is the realm of biologists, ornithologists, and zoologists; my one remark on the taxonomy issue is that the vast majority of the extinctions here are of subspecies, not full species.   

The spatial patterns are remarkable, however.  Be aware that the dot hotspots are only what I can find documentation for at present; I have little doubt that there are many more.  Note the concentrations on islands, at lower latitudes, and in proximity to the oceans.   These strong tendencies cannot be mere coincidence.  Note also that, for the most part, the concentrations of extinction do NOT coincide with the spatial concentrations of human occupancy; it is the fringe areas of recent or occasional human contact where the losses are greatest.       [BACK]

Of the lists for several hundred historically extinct birds and mammals , nearly all had several of the following characteristics that rendered them helpless:

• few defensive traits (often because of few natural enemies)

• low mobility (flightlessness, slow motions, few dispersal mechanisms, etc.)

• high visibility (large size, vivid colors or patterns, attractive motions, etc.)

• docile nature (tame, fearlessness, inquisitive)

• small population (often dictated by small available area)

• small or unique habitat area

• isolation, especially over long periods of time

• slow reproductive and maturation rates

• extreme niche specialization

• low resilience to disturbance       [BACK]

There are now two additional threats, however, both due largely to human actions.  The first is importation of disturbance-adapted foreign competitors.  The second, and only recently receiving much recognition, is genetic alteration and hybridization.   Either of these poses the prospect for pushing even more endangered organisms over the brink into extinction, including those that survived direct exploitation and habitat modification.      

The documentation is far less complete for other taxonomic classes, but extinction is probably as frequent among these, if not more so.  I have compiled very small example lists, with the caveat that these have even less veracity than the bird and mammal lists, for the following:

Much further work remains for these others, including maps.  Note that nearly all of these are of North American organisms; surely this is not the actual geography of these losses.