Encyclopedia of Biological Invasions (Encyclopedias of the Natural World) by Daniel Simberloff & Marcel Rejmanek

Author:Daniel Simberloff & Marcel Rejmanek
Language: eng
Format: azw3
ISBN: 9780520264212
Publisher: University of California Press
Published: 2011-01-02T00:00:00+00:00

FIGURE 1 This figure describes demand for protection against invasive species in a particular country i by the citizens of that country and by the rest of the world. If exports from country i threaten other countries, the global community may be expected to wish higher levels of protection than the citizens of that country. It follows that in the absence of markets for global protection against invasive pests or pathogens, country i will undertake only enough protection to satisfy local demand and will equate the marginal local cost of protection with the marginal local benefits it offers. However, if the global community can express its willingness to pay for protection through direct payments, such as payments for ecosystem services, the level of protection can be increased to the point that the marginal local cost of protection is equal to the marginal global benefits. This is the socially optimal outcome.

CONTROLLING AND CONTAINING THE

DAMAGE DONE BY PROVEN INVADERS

At the national level, there is reason to believe that prevention is generally better than cure—that the costs of mitigating risk through port and pathway interventions are lower than the costs of eradication or control of established pests. Nevertheless, given the growing risks associated with globalization and trade growth and the limited set of options open under the GATT, countries increasingly have to identify options for the control of established alien species. Prevention (primarily screening to prevent introductions) and the control of established invasive species (eradication or containment) are substitute strategies. Reducing the cost or raising the effectiveness of one will increase its use relative to the other. It follows that the weakness of most defensive efforts to screen imports makes the eradication or containment of established invaders the default strategy.

In every case, efficiency requires balance between the marginal costs and benefits of the strategy. A well-known invasive species control program in South Africa, the “Working for Water” program, bases control of invasive Pinus, Hakea , and Acacia species on their impact on the water available both to other species in the fynbos system and to human users. Such measures of benefit provide a benchmark against which to assess the costs of the program. In the absence of information about the damage avoided through adoption of some control strategies, there is no way to judge whether the strategy is warranted. Indeed, this remains a general problem in invasive species control.

At present, the commitment of resources to the problem of invasive species appears to be increasing in most countries. During the 1990s, for example, annual spending on emergency eradication programs to avoid the costs of introduced pathogens in the United States increased from $10.4 million to $232 million. More recently, annual expenditure on invasive species in the United States has exceeded $1 billion. While this implies that expectations about the potential damage cost of invasive species are increasing in the United States, not all countries are raising expenditures on invasive species in the same way, and even within the United States, the signals are mixed.

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