There has been much heat and little light in the discussions over the impact of non-native species on natives, and on eco-systems in general. Many of the proponents of natives-only have exaggerated the situation and have presented a "revisionist natural history" which neglects the benefit that non-native species can have to eco-systems in general and specifically, plant/pollinator webs. New work is aimed at countering that trend:

> Non-native species can cause the loss of biological diversity (i.e., genetic, species, and ecosystem diversity) and threaten the well-being of humans when they become invasive. In some cases, however, they can also provide conservation benefits. We examined the ways in which non-native species currently contribute to conservation objectives. These include, for example, providing habitat or food resources to rare species, serving as functional substitutes for extinct taxa, and providing desirable ecosystem functions. 

> We speculate that non-native species might contribute to achieving conservation goals in the future because they may be more likely than native species to persist and provide ecosystem services in areas where climate and land use are changing rapidly and because they may evolve into new and endemic taxa. The management of non-native species and their potential integration into conservation plans depends on how conservation goals are set in the future. 

> A fraction of non-native species will continue to cause biological and economic damage, and substantial uncertainty surrounds the potential future effects of all non-native species. Nevertheless, we predict the proportion of non-native species that are viewed as benign or even desirable will slowly increase over time as their potential contributions to society and to achieving conservation objectives become well recognized and realized.

The Potential Conservation Value of Non-Native Species
MARTIN A. SCHLAEPFER, DOV F. SAX, JULIAN D. OLDEN
Conservation Biology
Volume 25, Issue 3, pages 428–437, June 2011

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