You know it’s hot when it’s too hot to ….

16 01 2014
© T. Brandon

© T. Brandon

My post’s title might be a good candidate title for a punk song in the 2030s (maybe by a re-incarnation of the Dead Kennedys).

I am currently sitting under my solar-powered ceiling fan as Adelaide is declared the world’s hottest city (and not in the funky, cultural, fun way), and I can’t help but contemplate climate change models predicting the fate of biodiversity over the coming decades. Because it’s far, far too hot to work outside, I’m perusing the latest interesting articles on the subject and I came across this recent little gem.

Also recommended on F1000Prime by Ary Hoffman, the paper, Using physiology to predict the responses of ants to climatic warming, by Sarah Diamond and colleagues touches on many aspects of climate predictions that need to be considered. I summarise these briefly here.

While no physiologist, I have dabbled in the past, although up until quite recently I didn’t see that physiology per se had much to do with conservation. It turns out that climate change has spawned an entire sub-discipline called ‘conservation physiology‘, which focuses inter alia on how species can/will/might respond and adapt to a warmer, climatically disrupted world.

What struck me about Diamond & colleagues’ paper was that yet again, it’s not as simple as heat-stressing a species experimentally and making a prediction on its future distribution (ecology is complex). No, the complexity comes in various forms that makes each species a little different from each other. Using North American ant species subjected to various warming scenarios in large (5 m) enclosures, they found the following: Read the rest of this entry »





Shrinking global range projected for the world’s largest fish

7 08 2013
© W. Osborn (AIMS)

© W. Osborn (AIMS)

My recently finished PhD student, Ana Sequeira, has not only just had a superb paper just accepted in Global Change Biology, she’s recently been offered (and accepted) a postdoctoral position based at the University of Western Australia‘s Oceans Institute (in partnership with AIMS and CSIRO). As any supervisor, I’m certainly pleased when a student completes her PhD, but my pride as an academic papa truly soars when she gets her first job. Well done, Ana. This post by Ana is about her latest paper.

Following our previous whale shark work (see herehereherehere, here, here and here), especially the recent review where we inferred global connectivity and suggest possible pathways for their migration, we have now gone a step further and modelled the habitat suitability for the species at at global scale. This paper sets a nice scene regarding current habitat suitability, which also demonstrates the potential connectivity pathways we hypothesised previously. But the paper goes much further; we extend our predictions to a future scenario for 2070 when water temperatures are expected to increase on average by 2 °C.

Sequeira et al_GCB_Figure 3

Global predictions of current seasonal habitat suitability for whale sharks. Black triangles indicate known aggregation locations. Solid line delineates areas where habitat suitability > 0.1 was predicted.

Regarding the current range of whale sharks (i.e., its currently suitable habitat), we already know that whale sharks span latitudes between about 35 º North to South. We also know that this geographical range has been exceeded on several occasions. What we did not know was whether conditions were suitable enough for whale sharks to cross from the Indian Ocean to the Atlantic Ocean – in other words, whether they could travel between ocean basins south of South Africa. Our global model results demonstrate that suitable habitat in this region does exist at least during the summer, thus supporting our hypotheses regarding global connectivity!

It’s true that the extensive dataset we used (30 years’ worth of whale shark sightings collected by tuna purse seiners in the three major oceans – data provided by the IRD, IOTC and SPC) has many caveats (as do all opportunistically collected data), but we went to great trouble to deal with them in this paper (you can request a copy here or access it directly here). And the overall result: the current global habitat suitability for whale sharks does agree well with current locations of whale shark occurrence, with the exception of the Eastern Pacific for where we did not have enough data to validate. Read the rest of this entry »





Ecosystem functions breaking down from climate change

17 05 2010

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.” Read the rest of this entry »





Moving forward with extinction risk predictions from climate change

15 10 2008

A little belated, but I thought this was worth mentioning for the Potential list…

182kydeee9pyxjpgOne from Keith and colleagues in Biology Letters entitled Predicting extinction risks under climate change: coupling stochastic population models with dynamic bioclimatic habitat models is a nice example of a way forward to predict the extremely complex array of ecological processes and patterns that may arise from rapid climate change.

One of the major problems with predicting how biodiversity might respond to climate change is the typical simplicity of single-species ‘envelope’ models – these models basically use tolerance limits (generally, physiological) or optimum conditions to predict how a species’ distribution might change. Unfortunately, this usually negates the complex dynamics of populations, the dispersal capacity of individuals, and interactions with other species that may all dominate possible responses. In other words, climatic envelope models may be way, way off (and probably vastly optimistic).

Keith and colleagues have brought us a step closer to better predictions of (and hopefully, better responses to) climate change effects on species. They linked a time series of habitat suitability models with spatially explicit stochastic population models to explore factors that influence the viability of plant species populations in South African fynbos, a global biodiversity hotspot. They discovered that complex interactions between life history, disturbance regimes and distribution patterns mediate species extinction risks under climate change.

Well done! Our next challenge is to incorporate multiple species’ interactions into such models (just to make them as mind-bogglingly complex as possible) to give us better approaches for managing our depauperate future.

CJA Bradshaw

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