A mountain vista in Colorado, with trees killed by pine beetles in the foreground. (Flickr: John B. Kalla)
Over at Nothing in Biology Makes Sense, I discuss a big new review article on all the ways understanding evolutionary biology will be critical for human health and development in the next hundred years:
The long list of authors, led by Scott P. Carroll and including Ford Denison, whose lab is just down the hall from my office at the University of Minnesota, explicitly connect evolutionary principles to global goals for sustainable development. These include the reduction of both “chronic lifestyle” diseases and infectious diseases, establishment of food and water security, clean energy, and maintenance of healthy ecosystems. Carroll and his coauthors divide the applications of evolution to these problems into cases where evolution is the problem, and those where evolution may offer the solution.
Over at The Molecular Ecologist, I discuss a new study that uses phylogenetic estimates for 17 families of vertebrates to estimate how rapidly those animals have evolved in response to past climate change, and compares those estimates to how fast they’ll need to evolve to keep up with projected climate change. Spoiler alert: past rates of adaptation to climate aren’t anywhere near fast enough.
To keep up with projected climate change, Quintero and Wiens estimated that the species in their dataset would have to undergo adaptive change at from 10,000 to 100,000 times faster than the rates estimated in their evolutionary past.
Well, but maybe. To learn whether the data are telling us what the study’s authors say they’re telling us, go read the whole thing.◼
Rosenau makes the case that when we (scientists/science supporters) talk to deniers/agnostics, conversations that begin in the scientific realm very quickly turn to religion, personal freedom, morality and even capitalism. The denial stems from how people identify themselves and how they see the world; it can be rooted in fear, anger and distrust of things outside their social group (religious and political affiliations are two major such groups). … The denial is not rooted in scientific facts.
With the ending of the ice age, which began around 21,000 years ago, many of these species experienced dramatic declines or went extinct. Woolly Rhinos, Mammoths, Glyptodon, and Megatherium went completely extinct, while Bison, Reindeer, Musk Oxen and wild Horse went through serious declines and range contractions.
These population declines roughly coincided with another major event in earth’s history, the global expansion of modern humans. Because of this synchronicity, there has long been debate about whether either is the cause. Did humans fuel their global expansion by hunting these animals to extinction, were they victims of a changing climate, or was it some combination of the two?
In the Duke University research forest, towers like these dosed experimental plots with carbon dioxide to simulate the effects of climate change. Photo by jby.
I arrived last evening at ScienceOnline 2011 barely coherent after thirteen hours of travel from Moscow, Idaho (2 a.m. Pacific time) to Durham, North Carolina (about 6 p.m. Eastern time). Robert Krulwich’s keynote address woke me back up. Krulwich explained his approach to science journalism and illustrated it with clips from his work, including the transcendently good Radiolab. How do you get your audience excited about science, according to Krulwich? Talk about what excites you, and lead them to discover it with you. I spent this morning touring the Duke University research forest outside Durham, where scientists from Duke and many other institutions are conduction some amazingly ambitious ecological experiments. Biogeochemist Ben Coleman presented studies of nanoparticle movement through terrestrial and aquatic ecosystems using mesocosms—semi-contained natural communities.
View inside an experimental warming plot. Photo by jby.
Carl Salk, a Ph.D. candidate in biology, walked us through plots that are being heated to simulate a changed climate. The plots are enclosed on four sides by plastic, with warm air pumped in via ductwork and electric lines warming the soil to bring them up to 3 or 5 degrees Celsius warmer than the outside. It doesn’t sound like much, but it makes a difference. Salk says plants in the warmed plots are developing leaves days and, in some cases, weeks earlier in the spring than plants in control plots.
The final stop was the biggest experimental setup, Duke’s Free Atmospheric Carbon Enrichment site, which has been testing how forests will grow in an atmosphere containing more carbon dioxide by pumping more carbon dioxide into forest plots. This is achieved with rings of towers like the ones pictured at the top of this post spraying carbon dioxide into experimental plots. The gas is reclaimed from fertilizer production, and into the air anyway; the experiment simply boosts it locally. The sheer volume of research done within these plots is amazing, but the site is now shutting down after 15 years.
The tour was over by noon, and the afternoon devoted to workshops. I attended a talk on how to develop course websites—with forums and online quizzes and integrated chat!—using Drupal, and another on the logistics of moving between blogging platforms. Once I’m done with this post, it’s off to a book-themed happy hour and dinner in Durham. Until tomorrow, here’s a slideshow of the other photos I’ve taken so far:
Regardless of what James Inhofe thinks, global climate change is going to dramatically reshape the natural systems our civilization depends upon. Unfortunately, even as we embark on the radical experiment of turning our planet’s temperature up to 11, we’re just figuring out what results to expect. A whole series of papers released in the last week exemplify this point, showing that living communities’ response to the changing planet may often be counter-intuitive.
Temperature stress may offset trees’ ability to soak up carbon dioxide. Photo by Wade Franklin.
Let’s start with the bad news:
A study out in last week’s PLoS ONE suggests that, rather than growing more rapidly and absorbing more carbon dioxide as the planet warms, forest trees may actually grow more slowly. More carbon dioxide in the atmosphere should generally increase plants’ growth rates, since carbon dioxide is the raw material for photosynthesis. On the other hand, rising temperatures may put plants under so much stress that it offsets the benefits of more carbon dioxide.
Silva et al. examined core samples from four tree species—black spruce, red pine, red oak, and red maple—growing in Ontario forests, and found that the trees’ growth rings were narrower in more recent years, as atmospheric carbon dioxide increased. Comparison of the growth rings to carbon isotope ratios (which capture a tree’s response to temperature stress) suggested that the growth declines were due to less hospitable temperatures. A large-scale historical study just out in Nature shows similar results for phytoplankton, microscopic photosynthetic organisms that form the base of ocean food chains. Working from historical records of ocean water transparency—phytoplankton makes water cloudy—going back to 1899, Boyce et al. found widespread declines in phytoplankton density [$a]. That’s bad news on multiple levels, implying that phytoplankton growth isn’t helping to absorb carbon dioxide, and that the oceans’ productivity is declining with its foundational food sources, not just from overfishing. (See also coverage of this result by the BBC and NPR.)
The rule of thumb for plants’ response to climate change has been that they’ll respond to warmer temperatures by starting the growing season earlier. But a new survey of plant populations in Florida finds that as global warming progressed, most species flowered later. The authors suggest that this is because many Florida plant communities that are already adapted to warm conditions, and because climate change across much of Florida has meant not just warmer temperatures overall, but also greater seasonal variation in temperatures—areas where summer temperatures increased also tended to have decreasing winter temperatures. Faced with the possibility of more late frosts, Floridian plants are waiting till later in the spring to start flowering.
Another weird result of climate change received lots of press last week: a thirty-year study of yellow-bellied marmots in Colorado found that, as their alpine habitats grew warmer, the marmots grew bigger and more numerous [$a]. Warmer overall temperatures mean earlier spring thaws, so the marmots are emerging from hibernation earlier, have more time to grow and pack on fat reserves before hibernation in the fall, and can make more babies the next spring. Is this good or bad? Co-author Dan Blumstein’s answer to that question in an interview with NPR is worth quoting:
I don’t know if I’m worried as much as I’m intrigued by it and I want to continue following the story. … it’s only through these long-term studies that we can gain important insights into what’s happening, what’s happened and ultimately identify mechanisms through which we may be able to predict what might happen in the future.
Climate change is essentially a global gamble, with the function of ecological communities everywhere as the stakes. Even as we humans are unable to muster the will to stop it, we’re finding out daily how many changes are on the way as the planet warms.
Boyce, D., Lewis, M., & Worm, B. (2010). Global phytoplankton decline over the past century. Nature, 466 (7306), 591-6 DOI: 10.1038/nature09268
Ozgul, A., Childs, D., Oli, M., Armitage, K., Blumstein, D., Olson, L., Tuljapurkar, S., & Coulson, T. (2010). Coupled dynamics of body mass and population growth in response to environmental change. Nature, 466 (7305), 482-5 DOI: 10.1038/nature09210
Silva, L., Anand, M., & Leithead, M. (2010). Recent widespread tree growth decline despite increasing atmospheric CO2. PLoS ONE, 5 (7) DOI: 10.1371/journal.pone.0011543
Von Holle, B., Wei, Y., & Nickerson, D. (2010). Climatic variability leads to later seasonal flowering of Floridian plants. PLoS ONE, 5 (7) DOI: 10.1371/journal.pone.0011500
Reading a pair of papers recently published in PLoS ONE, you might be forgiven for thinking that ecologists don’t know whether or not interactions between species matter. Both examine the effects of climate change on ecological communities — but where one assumes that species in a community are as interchangeable as bricks in a wall, the other concludes that the presence of competitors is pretty important.
First, Stralberg et al. attempt to predict what will happen to the birds of California under projected climate change. They constructed individual models of each bird species’ environmental requirements, and then figured out where those requirements would be met under a range of possible climate change scenarios. They find, not surprisingly, that this produces a lot of never-before-seen bird communities:
Our analysis suggests that, by 2070, individualistic shifts in species’ distributions may lead to dramatic changes in the composition of California’s avian communities, such that as much as 57% of the state … may be occupied by novel species assemblages.
But do species really move across the landscape as independent agents? It’s hard to believe that the do. Every species interacts with others — competitors, predators, prey, parasites — and presumably these interactions have some impact on where that species can survive.
That’s certainly what the other paper suggests. Adler et al. tested the effects of altered water availability (as a proxy for climate change: normal, supplemental, or drought conditions) and competition (normal or with competitors removed) on experimental plantings of three different prairie grass species. They found significant effects of both competition and rainfall on the plantings’ growth — although there wasn’t a meaningful interaction between the two factors. (That is, competition conditions didn’t alter the effect of water availability.)
There are actually a lot of studies suggesting that species interactions will be important in determining how communities cope with changing climates:
The prototypic example of this is the case of Great tits and the caterpillars they prefer to feed their chicks — warming climate means that the period when the caterpillars are most abundant is earlier and earlier each year, disrupting the tits’ breeding season [$-a].
A recently-published experiment transplanted butterflies from populations near the middle of their home range to sites at the northern edge to simulated climate-change driven shifts, and found that the availability of preferred host plants shaped how well the butterflies performed [$-a].
All of which is to say, we may not know how the species interactions within a particular community will shape its response to climate change, but there’s good reason to think that they will.
Adler, P., Leiker, J., & Levine, J. (2009). Direct and indirect effects of climate change on a prairie plant community PLoS ONE, 4 (9) DOI: 10.1371/journal.pone.0006887
Pelini, S., Dzurisin, J., Prior, K., Williams, C., Marsico, T., Sinclair, B., & Hellmann, J. (2009). Translocation experiments with butterflies reveal limits to enhancement of poleward populations under climate change Proc. Nat. Acad. Sci. USA, 106 (27), 11160-5 DOI: 10.1073/pnas.0900284106
Post, E., & Pedersen, C. (2008). Opposing plant community responses to warming with and without herbivores Proc. Nat. Acad. Sci. USA, 105 (34), 12353-8 DOI: 10.1073/pnas.0802421105
Stralberg, D., Jongsomjit, D., Howell, C., Snyder, M., Alexander, J., Wiens, J., & Root, T. (2009). Re-shuffling of species with climate disruption: A no-analog future for California birds? PLoS ONE, 4 (9) DOI: 10.1371/journal.pone.0006825
Visser, M., Holleman, L., & Gienapp, P. (2005). Shifts in caterpillar biomass phenology due to climate change and its impact on the breeding biology of an insectivorous bird Oecologia, 147 (1), 164-72 DOI: 10.1007/s00442-005-0299-6
One of the most-cited effects of global warming is that of rising temperatures on crops – hotter average conditions should lead to warmer, drier conditions, reducing yields in the best growing areas and maybe eliminating them where conditions today are marginal. In this week’s Science, a new study puts some numbers behind that speculation [$-a], and the news is not good.
Assembling the results of 23 climate models, authors Battisti and Naylor compare projected temperature ranges for the coming century with the ranges observed in the previous one. By the final decade of the twenty-first century, they say, summertime high temperatures in most of the continental U.S. have a 70% probability of exceeding the hottest summer temperatures ever recorded; in Saharan Africa, much of the Middle East and central Asia, the probability is 90-100%.
To put these numbers into perspective, Battisti and Naylor go to the history books, citing an array of cases in which local high temperatures have disrupted food production, creating regional shortages that eventually impacted worldwide food markets:
By comparison, extremely high summer-averaged temperature in the former Soviet Union (USSR) in 1972 contributed to disruptions in world cereal markets and food security that remain a legacy in the minds of food policy analysts to this day. … Nominal prices for wheat — the crop most affected by the USSR weather shock — rose from $60 to $208 per metric ton in international markets between the first quarters of 1972 and 1974.
Battisti and Naylor end by calling for substantial investment in adaptation measures to prevent “a perpetual food crisis.” Increasingly, this looks like the only practical course of action – although reducing and eliminating man-made greenhouse gas emissions is critical, turning global climate around is going to be like steering an aircraft carrier, and it’s going to get pretty warm before we turn the corner.
Belding’s ground squirrels contracted their high-altitude range as climate warmed. Photo by infinite wilderness.
Moritz et al. repeated a survey of small mammals – chipmunks, shrews, ground squirrels, and the like – originally conducted by the biologist Joseph Grinnell between 1914 and 1920. Since that time, average minimum monthly temperatures in the Yosemite area have increased approximately three degrees Centigrade (five and a half degrees Fahrenheit), and Moritz et al. found significant changes in the distributions of small mammals associated with that warming.
In the face of warming temperatures, the easiest thing for animals to do is move up to the cooler climes at higher elevations, and this is what many species did. Those at lower elevations expanded their ranges uphill. But small mammals already living at high elevations, like the aptly named Alpine Chipmunk (Tamias alpinus) have nowhere cooler to go – so their ranges contracted over the last century. As the globe warms up, this pattern is likely being repeated in ecosystems everywhere – not a happy prospect for critters that live at high elevations.
C Moritz, JL Patton, CJ Conroy, JL Parra, GC White, SR Beissinger (2008). Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA. Science, 322, 261-4 DOI: 10.1126/science.1163428