Too much snow

I spent today waist-deep in snow because of the interactions between the climate system and the airfare pricing system. A long time ago I planned a summer of fieldwork meant to focus on how alpine plant communities changed over a growing season – the followup to last year’s project installation. Alpine plants begin seriously growing – producing leaves, growing stems making flowers – once the snow has melted, although a few species manage to start growing under the snowpack. That meant I needed to plan an arrival at the field site that was early enough to catch the beginning of the growing season, but not so early I would waste time waiting for meters of snow to melt.

summer start 0

So a few months ago I made a gamble. The California drought was symptomatic of a very dry climatic pattern over the Rocky Mountains, so I imagined a dry winter with an early snowmelt. And I imagined rapidly increasing airfares from Europe. So I took a chance on an early June arrival. All perfect until May turned out to be one of the wettest on record, with extensive snowfall at high elevation – and fresh snow too, not covered in a whole winter’s worth of dark-colored dust that would hasten the melt.

summer start 1

You can see my research site in the upper right of this photograph – to the left of the dark-colored ridgeline, apparently well-covered. But sometimes aerial photographs distort the truth, and local variation in substrate and sun exposure lead to faster melts. I knew that my site was on a south-facing ridgeline, and not too far away from one of the dark patches indicating bare rock. Maybe its growing season might be underway.

Today I took my field assistant on a long hike into the mountains to scout out the area. We were aiming to reach 11800′ elevation.

summer start 3

Unfortunately the snow was exactly where the aerial photo showed it to be. We spent a fruitless afternoon falling waist-deep into loose snow on forested steep slopes before giving up at about 10500′. Too dangerous, and very little chance that anything would be growing.

summer start 2

Tomorrow we build instruments, assemble gear, and find snowshoes. Then we wait. And finally we will head up the mountain again, ready to welcome our plants to the summer.


Towards fossil fuel divestment

I think that universities can play a unique role in leading public conversations on controversial issues. A university is a city on a hill, a place where light cannot be hid. It is a place that can lead by example and set precedent for others.

I have been thinking about this role because two institutions I have been closely associated with have now taken divergent paths. The issue in question is fossil fuel divestment. Should a university’s endowment and other funds be used only to maximize long-term returns to support the overall institution, or instead to also be used as instruments of social change and leadership? In particular, should a university with goals of building a more just and verdant future be supporting investments in an unsustainable industry that directly causes both economic growth and harm to people and the environment? There are clearly good arguments on either side, but I do think that some social issues stand out from others in terms of their generality and urgency – and climate change and the role of fossil fuels should be one of them.


Right now I am working for the University of Oxford, where an active student campaign has been pushing for divestment for some time now. Since moving to England I have been following their actions, but had been surprised by the limited level of support and awareness the cause has found among students and the community. The photo above is from Radcliffe Square on the day of a protest and awareness event; aside from a wonderful and dedicated group of organizers, hardly anyone appeared. Compare the same location two weeks earlier, when thousands of people populated the square to celebrate nothing more important than the first day of May. But in the wider community, many prominent academics have signed on, including several in my own research group.


Earlier this week, the university’s Council took a decision on their investments. Despite student pressure, I didn’t expect that anything would come of the meeting. But I was pleasantly surprised that the students’ hard work had been worthwhile. The university re-affirmed their commitment to socially responsible investing. They are committed to a policy of no direct investment in coal or oil sands, and to minimizing overall exposure to the energy sector. But they did not divest from extant holdings in these sectors, and as far as I can see have made only vague statements with regard to engaging on the issue in the future, or with regard to making more direct changes. It is a good start, and one that generated some international press coverage, but not one that conclusively resolves the issue. I am cautiously optimistic about the university’s commitment to leadership on this point.

I was much more disappointed by the choices made by my own undergraduate institution, Swarthmore College. It is a Quaker school, one whose founders included many prominent abolitionists and suffragists, and one whose ethos is ostensibly committed to moral leadership. It is also the birthplace of the fossil-fuel divestment movement and the alma mater of the United Nations’ climate chief, Christiana Figueres. Students had been putting pressure on the administration to make a similar commitment to divestment, but the institution’s board of managers took a decision in early May to not divest, and only to offer a chance for future donations or income to be allocated to fossil-fuel-free funds. The decision was covered by several international news outlets, but too late to effect change. It was a disgraceful retreat, and in my opinion a lost opportunity for leadership.

I have added my name to campaigns at both institutions, and have committed to withhold any donations to the latter until this policy changes. In my personal life, my savings are invested in broad market-tracking funds, but this summer I plan to sell them and change that. These are small nudges, but small nudges can lead to big changes, just as university divestment can encourage public conversations about the topic in the broader world.


Citizen science in the woods

wytham bluebells

A few miles distant from Oxford are Wytham Woods. This forest has become one of my favorite places to visit, a quiet place reachable by a few miles’ cycling over canals and country lanes. In spring the woods are painted with the flowers of bluebells (Hyacinthoides non-scripta). It is perfect for a solitary walk, but it is much more than that. Wytham is also home to a compelling set of research programs and citizen science initiatives.

Last Thursday I headed out in the early evening to go badger watching. Researchers have been studying the population dynamics of the badger (Meles meles) since the 1970s, providing a unique long-term record of thousands of individuals constituting a carnivore population’s dynamics, and of the social behavior of a charismatic species.

badger 1

Every spring the public is invited to go badger-watching in solidarity with this research.

badger 3

Badgers are charismatic icons of the English countryside, and have special status under the 1992 Protection of Badgers Act. They are the icon of a local conservation group I volunteer with, and our leader on this evening even happened to have a stuffed one with him.

badger 2

We piled into cars and made our way through the golden light of the day’s end, then picked our way into the forest.

badger 4

Badgers live in setts. These are large sets of underground tunnels and rooms that accommodate many individuals, and which are used year after year. From the surface they look like large mounds, with nearby trees used for scratching, and nearby forest sites used for toilets. They very clearly look like well-maintained homes. I settled in next to a pine tree on the downwind site of the sett, and began to wait.

badger 6

Badgers are predators of earthworms, insects, and most any other sort of grub or egg that can be found on the ground. They hunt at night, and have a keen sense of smell but a fairly limited sense of vision. I had no sight of any badger at all until the sun began to disappear over the horizon, and the day began to change into night.

badger 5

And then one made a first appearance, its head surveying the land above a tunnel entrance. I had never seen a live badger before – sadly only dead ones on roadsides. It had a very friendly and quick way of moving, almost playful. And then it was gone back underground, perhaps waiting for darker night, or for me to leave. Over the next few hours I was lucky enough to see glimpses of several more before the chilly air and my own hunger took me away. Being unable or unwilling to predate earthworms, I headed back to the city, happy for this small glimpse of the life of another species.

What impressed me most about the night was the large turnout of people who felt strongly enough about badgers and forests to spend a night shivering in the darkness looking for them. I have never seen such an enthusiastic turnout for this kind of citizen science, or this kind of bridge-building between researchers and the public. I think there is a lot of power in this kind of low-effort, high-fun engagement. Admittedly the the group was not very diverse – mostly older people and younger parents with small children, and nearly all white – but it was still a large one. Inclusivity and diversity seem to be challenges that span nations. Regardless, the night was an inspiration and a challenge for my own future outreach work.

Chasing a temperate spring


The spring blooms of the North American desert are long since over, but the same cannot be said everything. In England, spring is just arriving, in a tumult of wind and fog and rain and the occasional bright sunny day. I just moved across one continent and one ocean and have been given the distinct pleasure of experiencing spring twice.

Here are two small scenes from my second spring.

brassica rapa

First, a field of rapeseed (a.k.a. canola, or Brassica napus). The crop flowers in early spring, and turns entire landscapes a brilliant shade of yellow. This kind of monoculture agriculture often has immediate downsides for local biodiversity and provisioning of ecosystem services like pollination. It is a high price to pay for the beauty of these brightly painted fields.


Second, a Japanese cherry (Prunus serrulata) in full spring bloom. The species is commonly planted, and in spring they cover the ground with a carpet of soft petals. On my first trip to a tropical rain forest I was very impressed by the wide number of species that bloomed before putting out leaves – it took a long time before I remembered that many temperature species like cherries take the same strategy. In the days since I took this photo, the flowers are gone, and bright green leaves have already flushed and begun to expand.

I will probably get a third spring when I head to the Rockies for summer fieldwork – I am effectively journeying to places with longer winters and delayed phenology faster than the planet’s annual orbit cycle can bring warmer conditions to them. It is my favorite part of year, and I am lucky to get to see it so many times.

New paper on ecological disequilibrium

Think of a community populated by saguaros, prickly pears, and agaves – do you imagine a warm place or a cold place? These species are warm-adapted, so a guess that the community is warm is a reasonable one. But what if the community were actually cold and snowy, like below? This would reflect ecological disequilibrium, a mismatch between the niches of species and the climate observed in a community.


Disequilibrium seems unreasonable – we do not expect to find bananas growing in Siberia – but it is not impossible. And this possibility challenges several areas of ecology that we all rely on. Computer models projecting species’ geographic distributions in the future assume that species have an instantaneous response to environmental change; similarly, paleoclimate reconstructions based on fossils or pollen also assume that communities’ past compositions reflect past climates.


Rapid climate change or slow species change can result in disequilibrium. Species may persist in place even as the climate changes away from their physiological tolerances; alternatively, a rapidly changed site may remain un-colonized by physiologically appropriate species because they have not yet had the time to disperse there, e.g. after glacial retreat following the last Ice Age, as seen above. These are just a few of the possible scenarios that can result in more modest versions of the Siberian banana or snow-covered agave scenario. But how would we know if they were occurring?

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We just published a new paper in Ecology (PDF reprint here) that explores ecological disequilibrium. We build a mathematical framework that lets us measure the strength of disequilibrium in a community, then test the framework in hundreds of forest communities across North and South America (data from BIEN). It comes with an associated R package, comclim, that lets other investigators assess disequilibrium in their own datasets.

What did we find? That most communities are actually in equilibrium with present-day climate. This is re-assuring for the assumptions of many current ecological models. But we also found that about a quarter of the communities we examined show strong lags with respect to present-day climate. We were unable to find strong explanations for why this subset of communities were out of equilibrium, providing an important problem for future research to focus on. We also found that disequilibrium will only become stronger under future climate change scenarios, suggesting that some of our equilibrium models will require modification in order to make accurate predictions for the future. Overall, I think the paper shows that communities’ response to climate change can be lagged and idiosyncratic, a message that underscores the complexity of interpreting past ecological change or predicting future change.

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This paper did not come together in a simple way. It began as an idea of mine to better reconstruct paleoclimate from species occurrence data, an idea that was funded by the Danish National Research Foundation and that ultimately sent me to visit the Center for Macroecology, Evolution, and Climate in Copenhagen. I originally decided to go not because of the science but because I wanted to escape a difficult personal situation at home. Once I arrived, my hosts and I soon realized that our proposal was not viable, as it assumed a level of ecological equilibrium for which we had no evidence. We re-oriented the project towards measuring disequilibrium instead. It took two years of visits to Denmark to finish major work on the project, and countless rounds of revisions and peer review to get it published. Three years later we have a product that I am proud of, and that bookends several important chapters in my life. I don’t think that the me who wrote the original proposal would quite recognize the me or the final paper that came out of this adventure.

I hope you’ll give the paper a read and see if it challenges you to think about climate change in some new ways!

Traveling back in time

After six years of living in Arizona, I had never visited the Grand Canyon. That finally changed this year. It was a marvelous ecological experience. The descent into the canyon is a journey back in time that ultimately reaches basement rocks that are nearly two billion years old. And it is also a journey through climate space, from the cold forests of the rim to the warm deserts of the river.


The top is covered by conifer forests – pictured here is the Colorado piñon (Pinus edulis).


Five thousand feet of elevation change covers a temperature differential of at least ten centigrade degrees. Looking down from the top, it is hard to imagine such a radical climate change could be tucked into the narrow bottoms of the rock layers.


But things change – here, about halfway down, western redbud (Cercis canadensis, blooming magnificently in purple) and other less hardy species begin to appear.


Further down the narrow side canyons begin to transport surface water. Dry ridges host warm desert-adapted species like Agave utahensis, but the wetter areas are able to support riparian species like cottonwood (Populus fremontii).


And then, magically, the river appears – the hidden architect of the canyon, the gathering place of water from these narrow side-canyons and also for hundreds of miles in every direction.


Walking alongside the river from its banks, I was impressed by its force as an ecological actor – to provide life and take it from such a wide portion of the continent, to cut down five thousand feet of rock in a few scarce million years, to so provide habitats for such diverse species, and to serve as a dispersal barrier for the many animals and plants (and people) stranded on either side of the rim.

Visiting the canyon after six years of thinking about ecology was undoubtedly a richer experience than if I had gone on the first day I moved to this part of the world. It is a marvelous teacher, and one that I am sure will continue to teach me.

Should ecologists stay home?

aa Since 2011 I have logged at least 152,590 air miles. This corresponds to 98,300 kg of carbon emissions at an approximate conversion rate of 0.2 kg C / km (LIPASTO 2009) – and probably more significant when accounting for radiative forcing (IPCC). Almost all of this has been work-related travel – journeys to field sites, trips to conferences, and transitions to new jobs. Carbon emissions have been one of the major costs of my work to better understand ecology and climate change. And I know I am not alone.

Is it all worth it? It’s an important question, and one that I have been thinking about for the past few years as my travel has accumulated. A recent paper by the Tyndall Centre for Climate Change Research (Le Quéré et al., 2015 – covered by Nature) calls for scientists – especially environmental scientists – to reduce the amount of flying we do in our work. They argue that scientists need to lead by example – we fly far more than most people do, participate in the public conversation on climate issues, and so have an important opportunity (or moral responsibility) to make more environmentally friendly choices. Why should we be exempt from contributing to the emissions targets our countries have set? Is trust lost in the scientific community when it does not abide by its own proscriptions? jet Flying less is a difficult proposition for me, for many reasons that are thoughtfully outlined in the Tyndall Centre paper. I have fieldwork in other countries or remote areas that are nearly impossible to get to via other methods, or would take sufficiently long intervals that my work would no longer be feasible. For example, reaching South America from North America is nearly impossible without air travel, because there is no road or train line that crosses eastern Panama, and boat travel takes weeks. In order to share my research, build collaborations, and get new ideas, I have to attend conferences and meetings, which are rarely close enough to home to be able to reach by other means. For example, my last job offer was the lucky outcome of a chance meeting at a conference – at a drinks session I would have not been able to attend virtually, and at a destination that would have taken four days to reach by train. I lose all of these benefits by not flying.

Yet, maybe I should. Maybe I should re-orient my science to have a more local focus, choosing field sites that are nearby, and only attending meetings that I can reach by public transit. I could rely on collaborators for foreign work, and attend far-away meetings virtually. I try. I took a Greyhound bus to my last job interview. The other year I was living in Copenhagen and was invited to give a talk in Aarhus – so instead of even taking the train, I cycled there. But it took a whole day that I could otherwise have used for working. If I took this minimalist approach to all my work, I might soon have very little work left. bike I think there is an essential issue with the kind of work that ecologists and climate scientists do. Tropical forest ecology requires tropical forest ecologists. That is, knowledge and change do not come freely; rather, they come at the cost of hard work, and that work often has a large carbon cost. Our carbon emissions are hopefully a price that we pay to invest in our futures.

But I do think we can do better. I agree with nearly everything the Tyndall Centre report outlines. We can develop local capacity, so fieldwork and projects are led by local scientists rather than foreigners. We can focus our work closer to home. We can travel only for essential fieldwork or conferences, putting off opportunities where our contribution will be small. We can do better on supporting virtual meetings, and locating physical meetings in countries that minimize total emissions (e.g. the International Biogeography Society).

I am still thinking about my own choices. I have already said no to several international conferences this year, attended one virtually, and am trying to concentrate most of my fieldwork within a thousand miles of where I hope to eventually have a permanent home. But this year I am still going to cross the ocean several times for different obligations, and still will go to some tropical sites so that I can know them by the time I write about them. It’s a start. field I hope I am investing my carbon emissions wisely.


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