ConservationBytes.com

I’m particularly proud to present to ConservationBytes.com readers a new paper we’ve just had published online in Journal of Animal Ecology: Mechanisms driving change: altered species interactions and ecosystem function through global warming (Lochran Traill, Matt Lim, Navjot Sodhi and me).

It wasn’t easy to write a review discussing climate change effects on biodiversity, mainly because so many have been written already and we needed to examine the issue from a fresh perspective. The evidence for single species’ responses to rapidly shifting climates around the world is overwhelming (see for a few thousand examples, see the following: Stenseth et al. 2002; Parmesan et al. 2003, 2006; Roessig et al. 2004; Thomas et al. 2004; Poloczanska et al. 2007; Skelly et al. 2004; Dunn et al. 2009). It’s rather remarkable how many things are moving in response, with reduction in range size being more common than expansion.

However, predicting extinction risk from climate change is far more problematic because traditionally there have been too few data on species interactions to make heads or tails of a particular species’ eventual response (e.g., see comment on Chris Thomas’ famous paper regarding this matter). As systems heat up, some species will change in abundance, thereby affecting the abundance of others (think predators and prey, pollinators and their host plants, etc.) – this whole complicated process combined with single-species’ responses makes predicting what a future ecosystem might look like nearly impossible. Add in all the other ecosystem damage we’ve done from forest clearance, invasive species and over-harvesting, it’s a right mess.

It is for this reason we focussed on reviewing the links between species rather than on the species’ responses per se. We looked specifically at ecosystem function, that is, “the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen. ‘Function’ also includes ecosystem services.”

We first identify the mechanisms of change through global warming, including ecosystem processes (primary production, nutrient cycling), then ecosystem services, followed by life history strategies (survival and recruitment, phenological response, colouration, behaviour, range), and complementarity (pollination and seed dispersal, predator-prey interactions, competition, invasive species, parasites/pathogens and hosts).

In general, we conclude that increased temperatures will affect the interactions between heterotrophs and autotrophs, and between heterotrophs, with generally negative ramifications for important ecosystem services and potential for heightened species co-extinction rates.

It’s more than just a big list – we tried to highlight the existing examples of changes between species, and identify the types of functions that are most likely to change as warming continues. Our take-home message is certainly that ecologists must move forward and target specific interactions among species when measuring how climate change is affecting our natural systems. We need better monitoring programmes, experimental data and focussed hypotheses regarding interaction.

CJA Bradshaw

Traill, L.W., Lim, M., Sodhi, N.S., & Bradshaw, C.J.A. (2010). Mechanisms driving change: altered species interactions and ecosystem function through global warming Journal of Animal Ecology DOI: 10.1111/j.1365-2656.2010.01695.x