BOTANICAL EVALUATION OF THE GOAT ISLAND COMPLEX, NIAGARA FALLS, NEW YORK
It is important, for the purposes of assessing whether Goat Island can naturally sustain again a great, diverse and interesting vegetation, to explore the possible mechanisms which may have contributed to this unusual diversity, and mechanisms that contribute to diversity generally.
If one adopts the generality that the number of species on islands depends upon immigrations and extinction rates, it follows that Goat Island must have had a good deal of immigration of species to it, and a relatively low rate of extinction. Routes of migration to the Island include diaspores floating to it from upriver. Diaspores must come in with aquatic bird populations, such as Mallard ducks or Gulls. They arrive borne on the wind, especially in short jumps, which is one explanation for the high similarity of the native floras on the Canadian (upwind) and American sides (downwind) of the river. With the large, mobile population of visitors to the park areas around the Falls, and to Goat Island, the likelihood of exotic diaspores becoming available for colonization of the area is relatively high.
What the original effects of isolation from animal life were on the islands at the brink of the falls can only be conjectured. Diversity may have been encouraged due to the absence of permanent populations of destructive herbivores on the island, especially during the summer months, and the relative absence of human activity and its associated disturbances. Herbivores, such as rabbits and deer, could on occasion have reached the island in winter on ice bridges. According to Kalm (1770), on hearsay, bears "seeing deer on the island, occasionally try to visit them, but are with much growling compelled to change their course and go over the falls." Goat Island "is covered with tall trees, and is sometimes full of deer" who, trying to cross the river upstream from Goat Island are swept there by accident, or are swept over the Falls. A rabbit is depicted in a drawing of the Goat Island flora (16 Ann Rep Comm, 1900) although this may have been fanciful, or rabbits may have been introduced when the bridges were built in the nineteenth century. A young road-killed specimen of Eastern Cottontail (Sylvilagus floridanus) was collected from the Island in 1987 and is presently in the collections of the Buffalo Society of Natural Sciences. A group of three raccoons were sighted in recent years at the Three Sisters.
Ice jams at any point or points along the length of the upper river did occur, damming the river's flow such that the beds of whole sections of either channel were exposed and could be crossed. The water is shallow in places in the river channels at the Falls (formerly to 10 feet on average). Goat Island seems to never have supported more than populations of native rodents. Larger mammals came to the Island by misadventure, situations exploited by the native peoples who were attracted to the "number of deer, elks and other animals that tried to cross the stream but which were carried to this islet .... When the natives from the mainland saw a sufficiently large number of animals on the island, they waded across and killed them" (Kalm, 1770).
"It seems almost as though [the fauna of Niagara] could never have resorted, habitually, to Goat Island. The access to it of the elk, the red deer, the bear, the panther, the lynx, the fox, and the wolf, common enough in the neighborhood, must always have been difficult, and their return to the mainland almost impossible. At the present time the quadrupeds inhabiting the island are probably only three, the Black-squirrel, the Red-squirrel, and the ... Chipmunk" (Day, 1901). The Gray Squirrel (Sciurus carolinensis and its melanistic form are presently frequent on Goat Island. Chipmunks (Tamias striatus) and the entrances to their burrows may be seen today on the shaded northern slopes of the Island. A population of Fox Squirrel (Sciurus niger) has been found for several years on Goat Island (1985-89, Dr. R. Andrle, personal communication). This squirrel is so rare in western New York State that it is frequently reported as absent from the State (Collins, 1981). It might be instructive to observe populations of deer and other herbivores on another large island in the Niagara River above the falls and maintained as a sanctuary, Navy Island, to see what their habits and effects are. Sixty-four acres and natural conditions on the island were insufficient to sustain animal populations for long. Although Goat Island is said to derive its name from goats being kept on the island (Clinton, 1822), it is instructive that all the other animals introduced in the same or nearly the same year perished in their first winter. It is doubtful that these goats could have lived there long enough to seriously affect the vegetation.
As late as 1810 there was no bridge to Goat Island, for when De Witt Clinton visited the area in that year, he thought it would not be practical to put a State Prison there, as access to and from the island would be too easy: "I saw a man who had potatoes planted on it, and who visited it frequently. Stedman used to ride there on horseback" (Clinton in Campbell, 1849). In fact, the Legislature of New York declined a request for entitlement by Augustus Porter, submitted in 1811 because they intended to erect a State Prison or Arsenal there (Porter, 16 Ann Rep Comm, 1900). In 1819, Howitt noted that Goat Island was until "a short time ago, the secure eyry of a number of Bald Eagles; but the bridge exposed them to the intrusion of travelers, and they have totally deserted it" (Howitt, 1820). The first bridge to the Island was built in 1817 (Porter, 16 Ann Rep Comm, 1900).
According to Walter (1973) "plant species are capable of existing far beyond their natural distributional areas if they are protected from competition with other species." He also suggested "the natural limit of distribution of a particular species is reached when, as a result of changing physical environmental factors, its ability to compete, or its competitive power, is so much reduced that it can be ousted by other species." Species extinction rates within portions of their range then, must be more related to factors of competition with other plant species than with physical parameters. Since so many species appear to have been crowded within the Goat Island complex, some factor must have been involved to lessen the ordinary rate of extinction from competing plant species.
In addition to high numbers of species noted on the complex, the Goat Island vegetation was also noted for its extraordinarily high abundance, or high biomass, or high productivity. One might expect that vigorous growth of plant species would encourage competition between species, with correspondingly higher extinction rates, yet this does not appear to have been the case.
Some factor or factors in the Goat Island complex must have lessened the competitive advantage or power of some species, and increased that of others, so an equilibrium was reached favoring high species diversity and abundance. For example "The slope leading down to Luna Island is covered with small trees so overgrown by vines that one wonders how the trees can grow at all, yet they appear to thrive under the load" (Chamberlin, 1892). Although the "small trees" may, under ordinary circumstances, have been destroyed by the vines competing with them, they appear to have derived competitive power sufficient to keep from being killed, and this perhaps from conditions favoring physiological optima in the species involved.
The relationship of the physical characteristics of the environment to a species' viability is of secondary importance to the competition for sun, nutrients, etc. with other living elements with the same or similar requirements. If physical requirements are met with to an unusually satisfactory degree on the islands, there will be more vigor on the part of the biota. Since not every species has the same requirements as another, the physical characteristics of the environment on the islands must have been diverse enough to have contributed to the vigor of a variety of species with corresponding power of competition. And yet there must have been competitive checks on all species such that few species dominated the whole area.
Something must have at once lessened extinctions due to competition by more well-adapted species, and still contributed to optimal conditions for vigorous growth and survival of individuals, especially seen in tree species and the native grape. During the January storm of 1889, a Buttonball (Platanus occidentalis) tree was blown down. It was "five feet in diameter, the largest tree upon the reservation" (6 Ann Rep Comm., 1890); "by the rapids, on the American side ... and on Goat Island, grew some of the largest arbor vitae ... I ever saw, - some of them measuring seven feet round" (Howitt, 1820); "in few other places [than Goat Island] does the Wild Grape climb so high or spread so far or swell itself into such tree-like proportions" (Chamberlin, 1892); "on Goat Island ... we were shown a piece of grape-vine about six feet long, which must have averaged six inches in diameter" (G. W. Clinton in Zenkert, 1934).
These sizes may reflect their great age, or the availablility of nutrients or moisture or some other factor favoring growth. It is most probable that the effects of competition between plant species was mitigated by the sheer diversity and complexity of microhabitats available on the islands.
Disturbance regimes due to high windfall and ice trimming discussed for the island in the central woods and crest vegetation sections above tend to reduce the competitive advantages of typically dominant species, such as trees and typical riverside vegetation lost due to ice-scour, or species over bedrock or thin soil at the water's edge, which are intolerant of periodic inundation and excessive drying.
Factors contributing to stability or ecological equilibrium in plant communities include interspecific competition, dependence of one species on the attributes and presence of another, the occurrence of species "that complement one another either spatially or temporally so that every ecological niche is filled," "The natural community is thus saturated and invading species can gain no foothold, although they are much more successful if the state of equilibrium is disturbed" (Walter, 1973). It is this disequilibrium that is probably central to the nature of the unusual flora on the islands.
It is most likely that the greatest factors favoring the historic diversity and abundance reported for the Goat Island flora derived primarily from:
a) Topographic diversity. Diversity has been lost due to grading in the establishment of lawnscapes and ease of their mowing, grading for extensive and excessive road and pathways in the Reservation, and modifying natural surface hydrology. Reintroduction of additional substrates and uneven surfaces and boundaries, such as making irregularities in ballasted and riprapped areas to diversify force of river current favors the establishment of a diversity of shore-pant communities.
b) High and diverse natural disturbances, such as atmosphere-derived ice, river ice, and high winds. A century-long amelioration in regional climate has produced less cold-stress-related regimens on the Reservation. Establishment of the ice boom at Buffalo-Fort Erie has reduced the incidence of ice-scour. Surging of river volume has been normalized by river-volume control devices. Seriously low volumes in winter with ice removal from the river at the Three Sisters eliminates the disturbance that may have created conditions for establishment of the rare plant communities there. Loss of much of the river volume due to diversion, especially in winter, may again reduce water availability for optimum growth displayed at the turn of the century.
c) Areas experiencing high moisture regimens, particularly in the heavy spray zones. Loss of much of the river volume due to diversion, especially in winter, may again reduce water availability for optimum growth displayed at the turn of the century. The most serious effect may be excessive diversion at the Three Sisters.
d) Isolation from excessive disturbance: by herbivores or through human "clear-cutting" and lawnscaping activities. Catastrophic disturbance is presently only exhibited by maintenance activities.
e) Powerful dispersal (seed, spore) vectors: relatively high winds, abundant migratory wildfowl, strong river currents. Careful reestablishment of habitat for migratory and other birds will contribute to an increase in incomming diaspore material.
f) Rich source of diaspores from diverse plant communities: in nearby Ontario and areas on the American side near the Niagara River Gorge, in freshwater habitats in the Great Lakes Watershed system open to migrating birds, in rich plant communities in the upper Niagara River and along the shores of Lakes Erie and Ontario.
Both the State of New York and Province of Ontario and municipalities governing river-side areas should develop policies in their parks favoring species diversity. Without this resource it will become increasingly difficult for species to become naturally introduced into the Goat Island complex.
The numerous recently reported species of plants, such as the mosses Trichostomum crispulum and Weissia hedwigii, as well as taxa reported new to New York State in similar habitats in the nearby Niagara River gorge: Didymodon australasiae new to eastern North America, Pottia davalliana, new to New York State, Desmatodon porteri, only station for New York, as well as the rare lichens reported for the Reservation by Dr. Harris (see lichen section) show Goat Island and related habitats are still unusual areas for species colonization or persistence. The islands seem naturally quick to accept new species, and reluctant to let them go.
Additional rare plants still in existence on Goat Island and newly introduced (see discussion above and rare plant sections) show that Goat Island still has the intrinsic resources to promote an important flora, if natural processes are allowed to function.