Wednesday, May 27, 2015

Weird paper claims climate change helps biodiversity

ScienceDaily says a paper found that climate change has less impacts on biodiversity than land use has. My first thoughts were that it's plausible, that the negative effects are combined, and that the priority might depend on the assumptions. I tried to RTFA, but it was paywalled other than a long abstract. The long abstract, however, nearly contradicts ScienceDaily, saying climate change has a mostly positive effect on biodiversity. Weirdly, it said that the climate change effect on biodiversity distribution by altitude was a positive effect in its study area, when I'd think that all other things being equal, a species will find less land available to it as its habitat range moves from lower to upper areas.

So, after some waffling I forked out the six bucks for temporary access, and I now have thoughts. I should be hesitant to pass judgment as a total amateur, so qualify this accordingly, but the main issue I'm fixating on is that they examined a single watershed catchment of a small, steeply-sloped river (1700 square km, elev. 45m to 1700m) in rural China. Your classic watershed is pie-shaped, with more land as you move uphill, even though our planet's land surface isn't similarly shaped. I think their finding, that in their case climate change benefits biodiversity when it moves habitat ranges uphill, is an artifact of their study area's topography. I looked for any discussion of this disparity between their study area and the terrestrial world in general, and didn't see it.

Other thoughts:

  • It studies stream macroinvertebrates, just one specialized aspect of biodiversity, and is very dependent on projected changes in hydrology. I'm surprised to read the claim that one could do meaningful, quantitative predictions for future hydrology at a small scale. Maybe I shouldn't be.
  • Speaking of predictions, the paper ends its predictions in 2050. I'd guess wildly that 2050 is about when land use impacts would've hit their maximum for a rural part of China, but climate change impacts are just beginning. Extending the analysis to a full century might give a different sense about the negative aspects of climate change.
  • The paper discusses the issue of a "summit trap" where the species habitat hits the maximum altitude and then disappears, but apparently it just wasn't an issue in this study.

In summary, I have no sense that paper is denialist or the authors were skewing it in that direction, but the catchment area and 2050 timeline IMHO exclude applying this analysis to saying climate change is secondary to land use in impact, let alone that climate change has a positive impact on biodiversity.


Fernando Leanme said...

I'm so glad the thought police has concluded the paper isn't "denialist". It would imply the censorship system has unacceptable leaks.


This paper sounds like Humboldt 101- as a matter of biogeography, unless and until the vertically dispalaced species actually go extinct, the niche cascade opened by their retreat becomes a Darwinian invitation to radiation and hence , diversificaation of whatever lives downslope.

Aaron said...

What they are really saying is that when the environment changes, niches for new species open up. This is true.

It is also a polite way of saying that land development is disrupting current species.

My take away is; that in the near term, land use has more impact than climate change, and species are moving up, away from developed areas.

Hank Roberts said...

The spambot got even more clever, I think.
Although posting exactly the same thing many, many places is a clew.


Tibet and the South American Llanos and tepuis long ago became refugia for species in retreat from the last ice age -- an assortment of small furry creatures , and beetles like Apodius hoderi come to mind.

Dano said...

I'm not going to pay for it, but in general it is true that land-use changes are among the most harmful to surface waters. The changes are much more rapid than slow change, and slower nutrient flows are easier to adapt to. Not an alarming paper, one that just add a cautionary dimension to the literature.




Unknown said...

Definite weird paper. Climate change impacts are *already* in effect, but will be the main driver of most ecosystems by 2050. Also, recent work shows that temps are rising faster at higher elevations than at lower, just as temps are rising faster at the poles than at lower lattitudes, so i wonder if their models account for that.
"Summit trap" sounds interesting. In the desert southwest (CA, AZ, NM) the alpine tops of isolated ranges are called "sky islands" and contain isolated remnants of Pliestocene ecosystems. I imagine these places are changing rapidly.

Barton Paul Levenson said...

FL: I'm so glad the thought police has concluded the paper isn't "denialist". It would imply the censorship system has unacceptable leaks.

BPL: I'm so glad the anarchist bombers, by which I mean AGW denialists like Fernando, haven't blown up yet another hospital, by which I mean subverted the peer review process to sneak through yet another incompetent, lying pseudo-article.

Bernard J. said...
This comment has been removed by the author.
Bernard J. said...

The retreat of high-elevation species and ecosystems is at least as much a 'push up' from species and ecosystems below as it is the latter filling newly-emptied niches. This might sound like a pendantic distinction but it has profound consequences for management - not that humans have done anything of positive note in terms of 'managing' anything in the domain of climate change.

In Australia people might be familiar with the relic Gondwanan Nothofagus associations in Australia at around 1000 metres altitude. The southern beech are a keystone species for the communities and are sensitive to fire, whilst the eucalyptus associations that grow at lower elevations are much fire-more tolerant - to the point of enthusiasm. Nothofagus also struggle to thrive in warmer temperatures, and especially to reproduce via seed in these conditions.

These two traits mean that they are being well and trully challenged by other vegeation associations, especially with the warming that humans have produced since the Industrial Revolution. In fact, in geological terms these species marching rapidly toward extinction as can be seen, for example, with N. moorei here:

For those of us who have walked and worked in these beautiful, primal forests it's a tragedy and a travesty but I suspect that most of the world won't even blink when, in another century or two, these magnificent remnants from Gondwana are effectively forever lost.

Brian said...

Dano - yes, it's reasonable that under some/many circumstances, land use impacts could be worse than climate impacts, esp if your study period ends as early as 2050. What I find weird is the idea that climate impacts are actually beneficia.

T Goodwell - summit traps are definitely happening. Here in California, pikas are winking out as their habitat disappears from the summits of various mountain ranges they live on. "Assisted migration" is one solution pondered in conservation biology, but I think it's unlikely that we're going to spot and assist every species that needs help.

Hank Roberts said...

"... The danger that is clear and present remains what Briggs has called ‘the precarious state of thousands of populations that are the remnants of once widespread and productive species’. The emerging term for the phenomenon is ‘defaunation’. In their survey on wildlife losses, published in Science last year, Rudolfo Dirzo, a biologist at Stanford, and colleagues, reported that terrestrial vertebrates are showing a ‘25 per cent average decline in abundance’ and that ‘invertebrate patterns are equally dire: 67 per cent of monitored populations show 45 per cent mean abundance decline. Such animal declines will cascade onto ecosystem functioning.’
The worry about ‘ecosystem functioning’ reflects a growing emphasis among conservation professionals. As the new science of conservation biology came into its own in the 1980s and ’90s, focus shifted away from concern about the fate of individual species and toward the general health of whole ecosystems. How serious is the ‘trophic cascade’ that results from an apex predator being absent or scarce? …"