Most naturalists have probably harbored the fantasy of "rescuing" a piece of property that has long been used for agricultural purposes. In the dream we remove all livestock and cease any form of crop production. We might then passively allow the fields to follow nature's slow but sure scheme of succession, resulting--eventually--in the restoration of the old--or a completely new--ecological climax. Alternatively, we might decide to accelerate the process by actively restoring plants and animals thought to represent such a climax. There is indeed a great deal of this wishful thinking currently occurring in one of the most ecologically ravaged areas in the country--Texas' Lower Rio Grande Valley.
My version of that fantasy was recently subjected to some very harsh light upon reading a paper published by Henry S. Fitch in the Journal of Kansas Herpetology, entitled "Collapse of a Fauna: Reptiles and Turtles1of the University of Kansas Natural History Reservation" (available as a 35 Kb PDF file courtesy of the Center for North American Herpetology website). Dr. Fitch is one of those iconic nonagenarian herpetologists who has shaped the modern face of the discipline. The first superintendent and resident naturalist of the Reservation (now known as the Fitch Natural History Reservation, in his honor), Dr. Fitch has personally observed the long sequence of changes about which he writes.
At its inception in 1947 the 590 acre reservation had been working farm/ranch land, ". . . in an ecotone between the deciduous forests characteristic of the eastern United States and the grasslands of the Great Plains." Twenty-six species of reptiles (sensu lato) were known to inhabit the reservation in the earlier years, and despite its history of agricultural use, most populations of these animals seemed to be in good condition. In fact, Dr. Fitch, over the years published detailed ecological studies on most of them.
In the ensuing absence of grazing and fires, however, which had previously constrained the expansion of the forest into the grassland habitat, the forest succession has gradually overtaken most of the reservation--much to the detriment of its herpetofauna.
In this paper Dr. Fitch provides species accounts for twenty-two species affected by the succession, based largely on his own studies and observations of them. A shocking 45% (n=10) of the species completely disappeared from the area. Another 27% (n=7) decreased in numbers and/or distribution but were still present. Only three species, all aquatic or semi-aquatic, were not significantly affected by the forest succession.
In summary, Dr. Fitch concludes: "It is ironic that on this area dedicated to preserving the native fauna and protected from anthropogenic disturbances for more than half a century, nearly three-fourths of the herpetofauna was lost, or set back and severely reduced by the process of natural succession. The lesson to be learned is that management with some manipulations may be necessary to maintain suitable habitats for all species."
1 Turtles are now considered by some taxonomists to represent their own class, Chelonia, separate from the Reptilia.