ECOLOGICAL ISSUES

1. Won't all the dead goats cause an imbalance in the populations that feed on them?

As is the case when sudden increase in the availability of food occurs, species that benefit from this availability will flourish until the food becomes less available. However, the project is planning on a rapid knockdown of the goat population (e.g. 90% reduction within 4 months), meaning that the existing hawks will not be able to take advantage of the sudden increase in nutrient availability - i.e. almost all the nutrients will be recycled back into the environment before hawks can make use of them. Some insects will benefit temporarily. Any effects would be minimized by ensuring that the campaign is completed as quickly as possible.

2. What are the other species affected by the goats?

Goats are known throughout the world to eat just about any plant, and the same is true on Isabela. Most plants are at risk with the goats (including the tree fern under which tortoises seek shade and water during the dry season). Animals and insects that may depend on this vegetation for survival would also be at risk. On-going monitoring of birds, plants, insects, reptiles and mammals is taking place on Isabela to measure these impacts.

3. What other problems does northern Isabela have?

A hike up to the rim of Alcedo volcano, the best known of the islands four volcanoes, reveals tremendous erosion gullies created by the continuous movement of goats over their preferred trails. Soils that have taken hundreds of thousands of years to develop are suffering serious erosion problems for the first time. Male goats also tend to rub their horns along the bark of trees. As a result of this behaviour, they have turned what once was a dense forest of Cyathea (tree fern) into what looks like a grassland today. Black rats, feral cats and feral donkeys are other introduced species that exist on the island. Black rats prey upon native wildlife and outcompete the endemic rice rat for territory, driving it closer to extinction. Cats are thought to have a tremendous impact on native birds, and young iguanas, while donkeys, though much less numerous, have impacts similar to those of goats. While donkeys will be targeted also during the goat work, cats and rats are controlled using different strategies.

4. How is the island to be ecologically restored?

If the goats can be removed before the seed bank in the soil is depleted, then the area will recover by itself quite well. Some trees may need to be planted in areas where the seed bank has been destroyed already. As funds become available, further control and eradication work targeting other introduced species will take place. Eventually, Northern Isabela is expected to return to a state close to what it was before the arrival of humans, though this may take several decades.

5. How are goats so able to survive the harsh conditions of Isabela?

Goats specifically pick out plants with a high water content, this allows them to live in areas with no surface water. Also, in extremely dry times, goats are known to be able to drink small quantities of salt water with apparently few ill effects.

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