Project brief identifiers
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Isabela Feral Ungulate Eradication Project (I.P.)
1.1. Biodiversity Representation and Ecological Integrity: Isabela island is the largest in Galapagos and contains the greatest representation of the archipelago’s endemic biodiversity. Its total landmass (458,812 hectares) is greater than that of all other Galapagos islands combined. It is divided into two distinct units of nearly the same size – northern and southern Isabela, by a 12 km wide isthmus consisting of near impenetrable lava fields. This rugged isthmus effectively isolates the relatively pristine northern half of the island from more degraded southern area, which has had a permanent human settlement for nearly 100 years. The southern area has suffered local extirpations and serious population declines of native and endemic species due to the presence of wild cattle, pigs and goats and to the conversion of native habitats to agriculture. Aggressive invasive plants have also displaced local flora in many areas. Though work is being done in southern Isabela, it is mostly restorative in nature and long-term action is needed to reverse trends. Conversely, northern Isabela has remained almost free from human induced impacts, except for the presence of cats, rats, a very small number of donkeys and more recently, goats. No uncontrolled presence of introduced plants has been recorded. Beyond the presence of a small U.S. military base on its northern tip during the second world war, the area has had no human settlements since it was created about 3 million years ago. Given its size and relative isolation from southern Isabela due to the Perry isthmus, northern Isabela can still be considered the largest relatively undisturbed landmass in the Galapagos archipelago.1.2. Conservation Value: The size of northern Isabela is relevant to its importance in terms of conservation values. Annex G clearly shows the direct relationship between island size and biodiversity / endemism in Galapagos – larger islands have greater diversity. For this reason, protection of the relatively undisturbed biodiversity of northern Isabela is fundamental to protecting the conservation values of the Galapagos overall. All of the other large, biodiversity rich islands (with the exception of Fernandina) currently have permanent human settlements, or in the case of Santiago island, have known widespread negative effects due to the lasting effects of previous human settlements (feral goats, pigs, donkeys, plants).
2.1. Threat to Ecological Integrity. Goats have been identified as the greatest immediate threat to the ecological integrity of northern Isabela Island. Though rats and cats are aggressive predators, these have been on Isabela for many decades, perhaps centuries, and the negative effect of these species on global values over the next six years is much smaller than the devastating impacts expected from goats should nothing be done to reverse current trends. In addition, no known means of eradication exist for these species, making total eradication campaigns impossible at the present time. Site-specific control methods, however, will be tested for these species through the GEF Alternative (funded by UNF) and once adequately developed, full eradication campaigns will scheduled following successful eradication of goats. 2.2. Population Size. Goats were first observed in small numbers in the south of northern Isabela in the early 1970’s. By the mid-1990’s, their number had exploded to an estimated 50,000-75,000. The population is currently estinated at 100,000, constituting a good example of a mega-size population and of the management challenges that such scales present to invasive species control. Though still predominantly restricted to the two southernmost of northern Isabela’s four volcanoes, small numbers of goats have been sighted on Wolf (the third southernmost volcano) in 1999, indicating that they are moving north. Given past trends, goats are expected to continue moving north as population densities increase to the south and to eventually occupy the entire island’s suitable goat habitat, which consists of most of its vegetated zones. 2.3. Potential Damage. The extent of damage caused by goats on Isabela island was first documented by internationally acclaimed wildlife photographer Tui de Roy. Photos taken on the rim of Alcedo (northern Isabela’s southernmost volcano) in 1995 were compared to photos taken in 1991. During the four-year interval, goats transformed the densely forested landscape, key habitat for the largest remaining population of the giant Galapagos tortoise, into a desert of bleached tree trunks and dry grasslands. Currently, an estimated 40%-60% of northern Isabela’s suitable goat habitat remains free of goat populations (at least at densities likely to cause negative effects). The potential for damage is thus very high if an eradication campaign is not undertaken in the near future. The only other island on which large goat populations exist is Santiago. Goats have been numerous on this island for over 100 years. Here populations at densities that cause serious negative effects, exist throughout the island’s suitable goat habitat. Eradicating goats from northern Isabela island will have greater benefits in terms of protecting native and endemic species, rare populations, undisturbed ecosystems and non-human induced evolutionary processes than would a similar effort on Santiago island. Additionally, the negative effects on global conservation values due to goats on Santiago are considered to be much less than those on northern Isabela.
3.1. Control versus Eradication. In an effort to deal with the exploding goat population on northern Isabela, and with the support of the Galapagos community and funding from tourist donations, the GNP and the CDF joined forces to carry out regular goat population control hunts on Alcedo’s rim, considered to be the most sensitive habitat for the largest single giant tortoise population remaining in Galapagos (est. 5,000 individuals). Since 1996, on average, two hunts a year, consisting of 10-12 hunters on 10-day outings, have resulted in the elimination of about 15,000 goats annually. In 1997, both the GNP and the CDF concluded that though effective, these control hunts could only be considered as a temporary strategy to deal with the goats. It was evident that goat reproductive rates and population dispersal to other regions of northern Isabela island were surpassing the capacity of these two institutions to undertake control measures given their limited resources and the many other conservation demands that required prompt action. In addition, the permanent cost of control, both in monetary terms and numbers of animals killed, would eventually far exceed the cost of a one-time large-scale goat eradication campaign. However, though preliminary research revealed many examples of successful goat eradication campaigns on islands throughout the world, none had ever approached the scale being contemplated in Galapagos.In September 1997, the GNP and CDF organized a 10-day workshop in Galapagos to evaluate the feasibility of an eradication campaign on such a large scale. An international panel of experts was convened, consisting of goat eradication practitioners, managers of previous eradication campaigns, government, NGO and other representatives with experience in the matter. The workshop participants concluded that the eradication of goats from northern Isabela is feasible, as long as a commitment both in terms of funding and political/institutional support could be guaranteed from the outset and sustained through the campaign. The workshop also resulted in the production of a detailed strategy for the eradication campaign (CDRS, 1997). |