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Do non-native species count as biodiversity?

January 7, 2019

There have been calls for biodiversity and ecosystem assessments to count non-native species as well as their native counterparts as positively contributing to biological diversity. Daniel Simberloff, Gore Hunger Professor of Environmental Studies at the University of Tennessee and member of the Invasive Species Specialist Group of IUCN’s Species Survival Commission, explains why this approach is misguided and would hinder our ability to achieve international conservation and development goals.

Non-native species homogenise ecosystems and, in some instances, cause populations of native species to plummet to the point of local extinction. The true impact of non-native species on ecosystems may take time, even decades, to become obvious, by which point it is often too late to reverse negative impacts from these intruders. This presents a problem for the entire ecosystem, including the humans who rely on ecosystem services for their well-being.

Despite the impacts of non-native species, there have been controversial calls for non-native species to be counted equally with native species in biodiversity assessments.

According to influential international publications, such as the UN-mandated Millennium Ecosystem Assessment, humans rely on ecosystems for physical purposes (e.g. food), as well as spiritual and aesthetic reasons. Maintaining diverse ecosystems is therefore important to ensuring quality of human life.

Despite the potential long-term impacts of non-native species, there have been controversial calls in both popular science writing (Fred Pearce, The New Wild) and in the scientific literature for non-native species to be counted equally with native species in biodiversity assessments, for example in those used to track progress towards the Aichi Biodiversity Targets of the Convention on Biological Diversity (CBD). This negates the importance of the changes that invasive species make to ecosystem functions.

It is misguided and potentially disastrous to consider native and non-native species as equal from the standpoint of both ecosystem services and conservation goals.

Originally published on the IUCN website.

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