The social and economic impacts of the global climate

We have a new paper out in Science:

Social and Economic Impacts of Climate 

For centuries, thinkers have considered whether and how climatic conditions—such as temperature, rainfall, and violent storms—influence the nature of societies and the performance of economies. A multidisciplinary renaissance of quantitative empirical research is illuminating important linkages in the coupled climate-human system. We highlight key methodological innovations and results describing effects of climate on health, economics, conflict, migration, and demographics. Because of persistent “adaptation gaps,” current climate conditions continue to play a substantial role in shaping modern society, and future climate changes will likely have additional impact. For example, we compute that temperature depresses current U.S. maize yields by ~48%, warming since 1980 elevated conflict risk in Africa by ~11%, and future warming may slow global economic growth rates by ~0.28 percentage points per year. In general, we estimate that the economic and social burden of current climates tends to be comparable in magnitude to the additional projected impact caused by future anthropogenic climate changes. Overall, findings from this literature point to climate as an important influence on the historical evolution of the global economy, they should inform how we respond to modern climatic conditions, and they can guide how we predict the consequences of future climate changes.

Some more of my commentary on the paper is here.

click to enlarge

What is "drought" anyway?

I like the approach of linking reduced-form empirical results to detail process-based simulation models to get at underlying mechanisms:

The critical role of extreme heat for maize production in the United States
David B. Lobell, Graeme L. Hammer, Greg McLean, Carlos Messina, Michael J. Roberts & Wolfram Schlenker

Statistical studies of rainfed maize yields in the United States1 and elsewhere2 have indicated two clear features: a strong negative yield response to accumulation of temperatures above 30 °C (or extreme degree days (EDD)), and a relatively weak response to seasonal rainfall. Here we show that the process-based Agricultural Production Systems Simulator (APSIM) is able to reproduce both of these relationships in the Midwestern United States and provide insight into underlying mechanisms. The predominant effects of EDD in APSIM are associated with increased vapour pressure deficit, which contributes to water stress in two ways: by increasing demand for soil water to sustain a given rate of carbon assimilation, and by reducing future supply of soil water by raising transpiration rates. APSIM computes daily water stress as the ratio of water supply to demand, and during the critical month of July this ratio is three times more responsive to 2 °C warming than to a 20% precipitation reduction. The results suggest a relatively minor role for direct heat stress on reproductive organs at present temperatures in this region. Effects of elevated CO2 on transpiration efficiency should reduce yield sensitivity to EDD in the coming decades, but at most by 25%.

See David Lobell's explanation at G-FEED.

Help map agriculture in Africa

Lyndon Estes writes

I have been working with Kelly Caylor developing a crowdsourced crop mapping project that is ready for some user testing.  I have asked my network of friends to test it a bit, in the hopes that we can see how the system performs, and get some initial data to show at my talk on this project next week at AGU.  

His instructions:

Hello Friends, I am kindly requesting your help with a research project. Our goal is to use crowdsourcing + google satellite imagery to map crop fields in Africa. We have just developed our prototype, which connects users on Amazon's Mechanical Turk Service to our field mapping interface.  

So, if any of you had a few minutes to spare over the next few days and an Amazon account (it's very easy to register as a Mechanical Turk user if you have an account, and not much harder to get an Amazon account if you don't have one), I would be very grateful if you could join up and map a few fields. The link below is to our website, which describes the registration and mapping process further.  

This project will be a for-pay endeavor within a few weeks, but for this stage when we are still working out bugs, we are going through Mechanical Turk's testing site (workersandbox.mturk.com), which pays fake money. Once you have registered, please go to sandbox to look for our HITs (Human Intelligence Tasks).  

Your help and feedback will be greatly appreciated, both for development purposes and for providing some data that I can include in my presentation on this project (Tuesday in San Fran).  

Thanks, Lyndon 

http://mappingafrica.princeton.edu/

Wanted: smarter global agriculture

Closing yield gaps through nutrient and water management

Nathaniel D. Mueller, James S. Gerber, Matt Johnston, Deepak K. Ray, Navin Ramankutty & Jonathan A. Foley

Abstract: In the coming decades, a crucial challenge for humanity will be meeting future food demands without undermining further the integrity of the Earth’s environmental systems. Agricultural systems are already major forces of global environmental degradation, but population growth and increasing consumption of calorie- and meat-intensive diets are expected to roughly double human food demand by 2050 (ref. 3). Responding to these pressures, there is increasing focus on ‘sustainable intensification’ as a means to increase yields on underperforming landscapes while simultaneously decreasing the environmental impacts of agricultural systems. However, it is unclear what such efforts might entail for the future of global agricultural landscapes. Here we present a global-scale assessment of intensification prospects from closing ‘yield gaps’ (differences between observed yields and those attainable in a given region), the spatial patterns of agricultural management practices and yield limitation, and the management changes that may be necessary to achieve increased yields. We find that global yield variability is heavily controlled by fertilizer use, irrigation and climate. Large production increases (45% to 70% for most crops) are possible from closing yield gaps to 100% of attainable yields, and the changes to management practices that are needed to close yield gaps vary considerably by region and current intensity. Furthermore, we find that there are large opportunities to reduce the environmental impact of agriculture by eliminating nutrient overuse, while still allowing an approximately 30% increase in production of major cereals (maize, wheat and rice). Meeting the food security and sustainability challenges of the coming decades is possible, but will require considerable changes in nutrient and water management.

Global crop area data at subnational resolutions

Bob Kopp showed me a new data interface for global crop area-harvested assembled by the FAO (here). Not many crops have anything close to complete coverage, but this is strong progress. The site says the data are downloadable, but I haven't tried so I don't know how user-friendly it is.

The Global Food System and Water Crisis: 10 Science Papers from the Past Year

[This is the second in a four-part series of guest posts by first year students in Columbia's Sustainable Development program]

The Global Food System and Water Crisis: 10 Science Papers from the Past Year

By StephanieLackner, Xiaojie Zhang, Kayleigh Campbell

To get caught up on the latest research on the global food system and water crisis we did a survey of the must-read articles from the last twelve months.  The requirements to make our list were simple.  First, the article had to be from the Research Articles or Reports sections of Science or the Review, Articles, or Letters sections of Nature published between May 2011 and April 2012.  Then we picked the ones that we thought would have the most significant impact on humans, were the most immediate or critical concerns, or were the most unique solutions to the current crises faced.  And here they are…

Rockefeller 2012 Innovation Challenges

Anna points out that the Rockefeller Foundation (yes, that Rockefeller Foundation) has announced its 2012 Innovation Challenges.  They plan on awarding up to nine grants of  up to $100K for research proposals on the three following FE-appropriate topics:

• Decoding Data - How will you use data to create change that improves the quality of life of poor or vulnerable communities in cities?
• Irrigating Efficiency - How will you improve or scale agricultural water use efficiency?
• Farming Now - How will your idea encourage and support young people to enter and stay in farming?

The deadline is May 25th, and applications are here.

An unusual number of goodies in Nature this week

A special Outlook issue reviewing the challenges of malaria control:

Nature Outlook: Malaria (Open access)

The war against the malaria parasite has raged for millennia, and still claims hundreds of thousands of lives each year. Resistance is a growing issue — for both the parasite to current therapy, and the mosquito to pesticides. Past attempts to eradicate malaria have failed. What will it take to finally subdue this deadly disease?

Commentary on the ivory tower:

Global issues: Make social sciences relevant
Luk Van Langenhove

Excerpt:

The social sciences are flourishing. As of 2005, there were almost half a million professional social scientists from all fields in the world, working both inside and outside academia. According to the World Social Science Report 2010 (ref. 1), the number of social-science students worldwide has swollen by about 11% every year since 2000, up to 22 million in 2006. 

Yet this enormous resource is not contributing enough to today's global challenges, including climate change, security, sustainable development and health. These issues all have root causes in human behaviour: all require behavioural change and social innovations, as well as technological development.... 

Despite these factors, many social scientists seem reluctant to tackle such issues. And in Europe, some are up in arms over a proposal to drop a specific funding category for social-science research and to integrate it within cross-cutting topics of sustainable development. This is a shame — the community should be grasping the opportunity to raise its influence in the real world.... 

Today, the social sciences are largely focused on disciplinary problems and internal scholarly debates, rather than on topics with external impact.... 

The main solution, however, is to change the mindset of the social-science community, and what it considers to be its main goal. If I were a student now, I would throw myself at global challenges and social innovations; I hope to encourage today's young researchers to do the same.

Meta-analysis of a famous question:

Comparing the yields of organic and conventional agriculture
Verena Seufert, Navin Ramankutty & Jonathan A. Foley

Abstract: Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts1, 2. Organic farming—a system aimed at producing food with minimal harm to ecosystems, animals or humans—is often proposed as a solution3, 4. However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices5. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak-acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions—that is, with good management practices, particular crop types and growing conditions—organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.

Copyright Nature

And some interesting agent-based modeling from Nature Climate Change:

Emerging migration flows in a changing climate in dryland Africa
Dominic R. Kniveton, Christopher D. Smith & Richard Black

Fears of the movement of large numbers of people as a result of changes in the environment were first voiced in the 1980s (ref. 1). Nearly thirty years later the numbers likely to migrate as a result of the impacts of climate change are still, at best, guesswork2. Owing to the high prevalence of rainfed agriculture, many livelihoods in sub-Saharan African drylands are particularly vulnerable to changes in climate. One commonly adopted response strategy used by populations to deal with the resulting livelihood stress is migration. Here, we use an agent-based model developed around the theory of planned behaviour to explore how climate and demographic change, defined by the ENSEMBLES project3 and the United Nations Statistics Division of the Department of Economic and Social Affairs4, combine to influence migration within and from Burkina Faso. The emergent migration patterns modelled support framing the nexus of climate change and migration as a complex adaptive system5. Using this conceptual framework, we show that the extent of climate-change-related migration is likely to be highly nonlinear and the extent of this nonlinearity is dependent on population growth; therefore supporting migration policy interventions based on both demographic and climate change adaptation.

Americans do care about their climate... they just might not realize it

Climate Change, Crop Yields, and Internal Migration in the United States
Shuaizhang Feng, Michael Oppenheimer, Wolfram Schlenker

We investigate the link between agricultural productivity and net migration in the United States using a county-level panel for the most recent period of 1970-2009. In rural counties of the Corn Belt, we find a statistically significant relationship between changes in net outmigration and climate-driven changes in crop yields, with an estimated semi-elasticity of about -0.17, i.e., a 1% decrease in yields leads to a 0.17% net reduction of the population through migration. This effect is primarily driven by young adults. We do not detect a response for senior citizens, nor for the general population in eastern counties outside the Corn Belt. Applying this semi-elasticity to predicted yield changes under the B2 scenario of the Hadley III model, we project that, holding other factors constant, climate change would on average induce 3.7% of the adult population (ages 15-59) to leave rural counties of the Corn Belt in the medium term (2020-2049) compared to the 1960-1989 baseline, with the possibility of a much larger migration response in the long term (2077-2099). Since there is uncertainty about future warming, we also present projections for a range of uniform climate change scenarios in temperature or precipitation.

Social Impacts of Climate Change and Climate Variability

We had an excellent session at AGU last week, thanks to everyone who contributed. Here's a video of the talks, which are succinct, interesting and nicely delivered.



U53F : AGU Fall Meeting 2011 from American Geophysical Union on Vimeo.

Trophic level as a measure of economic development?

I will return this this new Nature article in another post, since it brings up a lot of interesting points, but I think this ancillary point was worth highlighting (even though the authors don't make this case): Looking at where humans sit in the food chain might be a useful (or at least interesting) measure of economic development.  In rich countries, land is used to feed animals that we eat.  In poor countries, people eat a higher fraction of crops themselves.  We've known about this phenomenon for a while now, but this map from the paper is striking because of its fully global perspective:

Here we show the fraction of the world’s total cropland that is dedicated to growing food crops (crops that are directly consumed by people) versus all other crop uses, including animal feed, fibre, bioenergy crops and other products. Averaged across the globe, 62% of total crop production (on a mass basis) is allocated to human food, 35% for animal feed (which produces human food indirectly, and less efficiently, as meat and dairy products) and 3% for bioenergy crops, seed, and other industrial products. There are striking disparities between regions that primarily grow crops for human consumption (such as Africa, South Asia, East Asia), and those that mainly produce crops for other uses (such as North America, Europe, Australia).
Copyright: Nature

AEA session for the winter meeting

Sponsored by Fight-Entropy! (not really...) The full preliminary program is here.


Jan 07, 2012 2:30 pm, Swissotel, Vevey 1 
Association of Environmental & Resource Economists

Environmental Constraints and Land-Use Decisions(Q1)

Presiding: MAXIMILIAN AUFFHAMMER (University of California-Berkeley)

When the Levee Breaks: Land, Labor, and Capital in the Deep South

SURESH NAIDU (Columbia University)

RICHARD HORNBECK (Havard University)

The Impact of Climate Change on Crop Choice in the United States

ROBERT MENDELSOHN (Yale University)

ZHIMIN LI (Yale University)

NAMRATA KALA (Yale University)

Climate and the Locations of Crops

SOLOMON HSIANG (Columbia University)

DAVID LOBELL (Stanford University)

MICHAEL J. ROBERTS (North Carolina State University)

WOLFRAM SCHLENKER (Columbia University)

JARROD WELCH (University of California San Diego)

Economic Impacts of Climate Variability and Climate Change: Evidence from a Quasi-Experiment with Great Lakes Water Levels

MICHAEL MOORE (University of Michigan-Ann Arbor)

HSING-HSIANG HUANG (University of Michigan-Ann Arbor)

Discussants:

JEFFREY VINCENT (Duke University)

JARROD WELCH (University of California-San Diego)

MAXIMILIAN AUFFHAMMER (University of California-Berkeley)

OLIVIER DESCHENES (University of California-Santa Barbara)

Heat

If you're in the continental US this week you've no doubt experienced one of the worst heat waves in a while. It's hitting 100 (Fahrenheit, sorry) in New York today and the same air mass broke records across the country as it slid east. To that end, here are a few explanatory science links to get you through your needlessly hot Friday afternoon:

• An excellent guide to NOAA's heat and humidity satellites
• A great overview of the insanity that was midwest weather this week (that and the previous link via boingboing's Maggie Koerth-Baker)
• Heat and public health from weather.gov
• Wikipedia's great list of historical heat waves
• A peak into the fascinating and contentious economic literature on heat and agricultural yields

Enjoy!

Agriculture under climate change

Ram pointed me to a nice feature article in the NYT from last week on the subject, featuring many researchers we know.

There's also a nice data graphic that they put together here. [In an earlier post, we provided the same SAGE dataset over the period1700-1990 for exploration in Google Earth]

Nature Climate Change Publishes first articles

Nature Climate Change is a new, high-profile and interdisciplinary journal focused on climate change research.  Its first research articles were released last week, abstracts below.

Nonlinear heat effects on African maize as evidenced by historical yield trials

David B. Lobell, Marianne Bänziger, Cosmos Magorokosho & Bindiganavile Vivek

New approaches are needed to accelerate understanding of climate impacts on crop yields, particularly in tropical regions. Past studies have relied mainly on crop-simulation models or statistical analyses based on reported harvest data3, 4, each with considerable uncertainties and limited applicability to tropical systems. However, a wealth of historical crop-trial data exists in the tropics that has been previously untapped for climate research. Using a data set of more than 20,000 historical maize trials in Africa, combined with daily weather data, we show a nonlinear relationship between warming and yields. Each degree day spent above 30 °C reduced the final yield by 1% under optimal rain-fed conditions, and by 1.7% under drought conditions. These results are consistent with studies of temperate maize germplasm in other regions, and indicate the key role of moisture in maize’s ability to cope with heat. Roughly 65% of present maize-growing areas in Africa would experience yield losses for 1 °C of warming under optimal rain-fed management, with 100% of areas harmed by warming under drought conditions. The results indicate that data generated by international networks of crop experimenters represent a potential boon to research aimed at quantifying climate impacts and prioritizing adaptation responses, especially in regions such as Africa that are typically thought to be data-poor.

Perceptions of climate change and willingness to save energy related to flood experience

A. Spence, W. Poortinga, C. Butler & N. F. Pidgeon

One of the reasons that people may not take action to mitigate climate change is that they lack first-hand experience of its potential consequences. From this perspective, individuals who have direct experience of phenomena that may be linked to climate change would be more likely to be concerned by the issue and thus more inclined to undertake sustainable behaviours. So far, the evidence available to test this hypothesis is limited, and in part contradictory. Here we use national survey data collected from 1,822 individuals across the UK in 2010, to examine the links between direct flooding experience, perceptions of climate change and preparedness to reduce energy use. We show that those who report experience of flooding express more concern over climate change, see it as less uncertain and feel more confident that their actions will have an effect on climate change. Importantly, these perceptual differences also translate into a greater willingness to save energy to mitigate climate change. Highlighting links between local weather events and climate change is therefore likely to be a useful strategy for increasing concern and action.

Cropscape Data Visualization

Micahel Roberts recently sent me a link to this relatively new data browser for land-use in the US, produced by the National Agricultural Statistical Service. Its not available for all years, but the resolution is impressive, allowing you to zoom in so you can see the individual fields of farmers.

The announcement of the dataset was here:

“CropScape delivers data visualization tools directly into the hands of the agricultural community without the need for specialized expertise, GIS software or high-end computers,” said Mark Harris, NASS Research and Development Division director. “This information can be used for addressing issues related to agricultural sustainability, land cover monitoring, biodiversity and extreme events such as flooding, drought and hail storm assessment.”

NASS produced the 2010 CDL using satellite image observations at 30-meter (0.22 acres per pixel) resolution and collected from the Resourcesat-1 Advanced Wide Field Sensor (AWiFS) and Landsat Thematic Mapper. The collection of images was categorized using on-the-ground farm information including field location, crop type, elevation, tree canopy and urban infrastructure. All prior CDL products dating back to 1997 are also hosted by CropScape.

CropScape was developed in cooperation with the Center for Spatial Information Science and Systems at George Mason University, Fairfax, Va. The research and development ofCropScape and the NASS partnership with George Mason University reflect NASS’s continued commitment to improve U.S. agricultural production, sustainability and food security. 

CropScape is operated by NASS’s Research and Development Division and hosted and maintained by the Center for Spatial Information Science and Systems at George Mason University. For more information about CropScape, and the Cropland Data Layer visit http://nassgeodata.gmu.edu/CropScape.