Tag Archives: Joshua tree

Climate change: bad for native plants

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[Correction/clarification appended]

This is how I can justify blogging as a scientific activity: once in a while, I find something really useful. Case in point is this post on the ‘blog of Pamela Ronald, the chair of the University of California Davis plant genomics program, which points to a new in the last volume of PLoS ONE that predicts (perhaps not surprisingly) climate change is going to be bad for rare plants in California.

The effect of climate change on plant communities is a major concern for me, because the range of my favorite woody monocot, the Joshua tree, may have to change quite a bit to compensate for a warmer climate. (For reference, see the photo of me setting up a pollination experiment on a Joshua tree in front of the Yucca Valley United Methodist church.) Previous projections have suggested that Joshua trees are going to be in trouble under a warming climate. Back in 2006, Science ran a cover article suggesting that climate change may make wildfires more frequent [$-a]. That’s a very real problem for Joshua tree’s range in the Mojave Desert – my lab has already lost field sites to brush fires in only about half a dozen years of focusing on Joshua trees. Another, more recent study has suggested that climate change is going to make the southwest U.S. even more arid&nbsp[$-a], which is also, obviously, a bad thing for plants (and people) in the region.

Earlier work of this sort usually modeled how climate change might increase or decrease the distribution of individual plant species – big, showy things like Joshua tree, Saguaro cactus, giant Sequoias. Loarie et al. improve over this by projecting changes in whole plant communities across the California floristic province. And they predict that up to 66% of plants endemic to California will lose more than 80% of their ranges. That’s a lot of diversity – more than just my study organism – at stake.

Correction:
In the original version of this post, I conflated the state of California, which does include a lot of Joshua tree’s range, with the California floristic province, which doesn’t. So Loarie et al.‘s new paper doesn’t directly impact Joshua trees. But it’s still cool/alarming, and decidedly post-worthy. In making that correction, I’ve also inserted a more recent study of climate change in the U.S. southwest, by Seager et al.

References:
Loarie SR, BE Carter, K Hayhoe, S McMahon, R Moe, CA Knight, and DD Ackerly. 2008. Climate change and the future of California’s endemic flora. PLoS ONE 3:e2502.

Seager R, M Ting, I Held, Y Kushner, J Lu, G Vecchi, H-P Huang, N Harnik, A Leetmaa, N-C Lau, C Li, J Velez, and N Naik. 2007. Model projections of an imminent transition to a more arid climate in southwestern North America. Science 316:1181-4.

Westerling AL, HG Hidalgo, DR Cayan, and TW Swetnam. 2006. Warming and earlier spring increase western U.S. forest wildfire activity. Science 313:940-3.

First Joshua tree article online

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The first publication from the Pellmyr Lab’s study of Joshua trees and their pollinators, in which we demonstrate significant, potentially coevolved, morphological differences in Joshua trees pollinated by different species of yucca moths, is now online at the American Naturalist’s website. My understanding is that it’ll be in the print edition this June.

Godsoe W, JB Yoder, CI Smith, and O Pellmyr. 2008. Coevolution and Divergence in the Joshua Tree/Yucca Moth Mutualism. The American Naturalist 171.

Hey! I know that tree!

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Tonight’s All Things Considered hits a long overdue topic as part of NPR’s ongoing “Climate Connections” series: the fate of Joshua trees in a warming world. I say overdue, of course, because two chapters of my dissertation will be on the population genetics and phylogeography of Joshua tree, and it’s hard to spend much time with Joshua trees and not wonder about how they’ll hold up under global warming.

I’ve spent two spring flowering seasons in Joshua Tree National Park, where much of the story centers. The Park is right at the southernmost boundary of Joshua tree’s current range, where (all else being equal) you’d expect to see the impact of warming earliest. As the NPR story points out, there does seem to be low recruitment (growth of young trees to replace old ones as they die) in the southern populations. On top of that, drier conditions are contributing to more frequent wildfires across Joshua tree’s range, and sprawl from Las Vegas and Los Angeles is rolling right through Joshua tree woodlands. The Park staff I’ve talked to (including naturalist Joe Zarki, who’s interviewed for the story) are seriously considering that they may have to take drastic measures to prevent Joshua Tree National Park from losing its namesake trees.