Center for Global Change and Earth Observations, Michigan State University, Manly Miles Building, 1405 South Harrison, East Lansing, Michigan 48823, USA.
Ecol Appl. 2010 Mar;20(2):303-10. doi: 10.1890/09-0193.1.
Urban areas are hubs of international transport and therefore are major gateways for exotic pests. Applying an urban gradient to analyze this pathway could provide insight into the ecological processes involved in human-mediated invasions. We defined an urban gradient for agricultural and forest ecosystems in the contiguous United States to (1) assess whether ecosystems nearer more urbanized areas were at greater risk of invasion, and (2) apply this knowledge to enhance early detection of exotic pests. We defined the gradient using the tonnage of imported products in adjacent urban areas and their distance to nearby agricultural or forest land. County-level detection reports for 39 exotic agricultural and forest pests of major economic importance were used to characterize invasions along the gradient. We found that counties with more exotic pests were nearer the urban end of the gradient. Assuming that the exotic species we analyzed represent typical invaders, then early detection efforts directed at 21-26% of U.S. agricultural and forest land would likely be able to detect 70% of invaded counties and 90% of the selected species. Applying an urban-gradient framework to current monitoring strategies should enhance early detection efforts of exotic pests, facilitating optimization in allocating resources to areas at greater risk of future invasions.
城市地区是国际交通枢纽，因此也是外来害虫的主要门户。应用城市梯度来分析这种途径，可以深入了解人类介导入侵所涉及的生态过程。我们为美国相邻的农业和森林生态系统定义了一个城市梯度，以（1）评估更接近城市化地区的生态系统是否面临更大的入侵风险，以及（2）利用这一知识来加强对外来害虫的早期检测。我们使用相邻城市地区进口产品的吨位及其与附近农业或林地的距离来定义梯度。利用 39 种具有重大经济重要性的外来农业和森林害虫的县级检测报告，描述了沿梯度的入侵情况。我们发现，拥有更多外来害虫的县更接近城市梯度的末端。假设我们分析的外来物种代表典型的入侵物种，那么针对美国 21-26%农业和森林土地的早期检测工作，可能能够检测到 70%的受入侵县和 90%的选定物种。将城市梯度框架应用于当前的监测策略，应该可以增强对外来害虫的早期检测工作，促进在未来入侵风险更大的地区优化资源分配。
