Abstract
Current conservation strategies are targeted at preserving species, without explicitly aiming at the maintenance of ecosystem functions. In a physically highly connected world, the unintentional relocation of terrestrial, marine, and microbial life is therefore unavoidable and has been an integral part of human evolution for thousands of years. Here, we challenge the default perception often shared among conservation ecologists that preserving native species at all costs and reducing the number of exotic species and their abundance is the only way to conservation and restoration success. While this strategy is valuable in cases where exotic species disrupt ecological function, there are examples where exotic species have similar functional traits to the threatened or extinct native species and can in fact help maintain the overall or target function of an ecosystem. In the race to cope with global environmental change, we argue that ecosystem function and ecosystem services need to be viewed not only through a taxonomic lens, but increasingly also through a functional, trait-based one.
Highlights
The definition of biological species rests on human-made concepts, in the realm of unicellular organisms (Hanage et al, 2005)
10 years after a debate weighing off the problem of nonnatives vs. the broader anthropogenic impact on our planet (Hulme et al, 2011; Thompson and Davis, 2011; van Kleunen et al, 2011), an increasing understanding of response and effect traits of both invasive and native species is urgently needed to support efficient decision making in conservation ecology
According to the simple rule “never change a running system” and without an exhaustive understanding of ecosystems, it is often argued that all species should be preserved in their natural habitat because one cannot be certain exactly which species provides which ecological function (Ehrlich and Ehrlich, 1981)
Summary
The definition of biological species rests on human-made concepts, in the realm of unicellular organisms (Hanage et al, 2005). “assisted colonization” or “re-wilding,” almost exclusively used for animals and while heavily debated (Ricciardi and Simberloff, 2009; Schlaepfer et al, 2009), attempts to replace extinct or struggling natives with an alien homolog This can work if the trait profile of the introduced alien is reasonably similar to the extinct species, and does not affect the overall community trait profile of an ecosystem (Figure 1B); this may change under altered environments (Figure 1E). A key functional trait of mountain forests is the protective capacity against rockfall, avalanche, and erosion, and alien A. altissima intruded forests in Southern Switzerland seem to be providing this function (and ecosystem service) similar to other tree species in the region (Moos et al, 2019) One of those species showing a similar decay pattern, and a similar potential decrease in energy reduction capacity against rockfall, is Castanea sativa (European chestnut). From a purely functional perspective, a newly introduced species should be assessed using the same criteria as species we may perceive as less “alien” because they have been around for longer
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