[This is the last in a four-part series of guest posts by first year students in Columbia's Sustainable Development program]
Climate Change and Sustainable Development: Key Contributions Since May 2011
By: Meg Sutton, Matthias Pfaff, and Anthony Louis D'Agostino
This past March, the US registered the warmest average March temperature on record, while more than 15,000 warm temperature records were broken. Far from an anomaly, global temperature records over the last two decades have been marching upward with "nine of the ten warmest years [occurring] in the 21st century."
Rising temperature trends, alongside other anticipated effects of climate change, will pose formidable challenges to development. To be effective, policy responses require the most current and reliable science available. Since this knowledge is continually evolving, we reviewed research published over the last year on the link between climate change and sustainable development, and have composed this summary of what we think will become key papers on this topic.
We reviewed all issues of Nature and Science published since May 2011 and searched through additional journals such as Climate Policy, Nature Climate Change, and Population and Environment. To be considered for this summary, papers had to present new findings based on rigorous research methods, which excluded many of the policy and viewpoint pieces in which climate change and sustainable development are central. Accordingly, we looked for papers that could readily translate scientific research into impacts on society. Pure climate science papers, such as paleoclimate reconstructions, were therefore outside our scope of review. The final six we selected can be grouped into three related categories: direct ecosystem service provision, species-level responses, and effects on human societies.
One category examines ecosystem service provision within the climate context. While tropical deforestation and land-use changes contribute a significant share of total greenhouse gas (GHG) emissions, Pan et al.  improve upon existing forest carbon flux inventories and find a global net annual carbon sink. By assembling data from newly available inventories and developing a series of statistical models, they find a slowdown in deforestation for the 2000-2007 period and an expansion in carbon sinks in temperate zones because of forest maturation in formerly agricultural lands and higher biomass density. Improving our knowledge of biological carbon sinks is required for informing scientific limits on emissions and determining forestry's role in mitigation instruments like REDD+.
A new piece in the open-access Environmental Research Letters by Xiao and Cai  offers projections of gross and net arable land areas for 2100. Combining global topographic and soil datasets with historical and projected climatic data from 13 general circulation models, they find highly heterogeneous effects across regions. Their results support existing studies that suggest northern zones, like Russia, China, and the US, will experience an expansion in arable lands, while tropical areas will likely face a contraction. Net global potential arable land areas, after accounting for increases in human settlements and protected areas, could see a 2-9% reduction over the current baseline.
Species-level responses to climate change constitute the second category of papers on our list. A group of British and Taiwanese researchers have reassessed  range shifts of different species in response to rising temperatures and found statistically significant positive correlations. Ordered in different taxonomic groups and regions, the median latitudinal and altitudinal migration distances were 16.9 km/decade and 11.0 m/decade, respectively. There is no significant lag in latitudinal species response, whereas there appears to be a significant lag in altitudinal response. Multiple geographic, ecological and physiological constraints are responsible for the range in responses expected across species. While the precise relationship of how these drivers interact has yet to be completely unpacked, Chen et al. find a near uniform migration away from rising temperatures. This has wide-ranging implications for the stability of ecosystems, biodiversity, and disease ecology.
Stationary species do not have the option of escaping increased temperatures and so are forced to adapt otherwise. As a recent study  has found, elevated temperatures constitute another source of stress to coral reefs – next to ocean acidification – by damaging carbon-delivering symbionts. Drawing together previous findings, the strongly heterogeneous and non-linear responses across taxa are attributed to a multitude of interdependent factors, including the speed of warming and acidification, the availability of genetic diversity, energetic constraints, and local physical and biological conditions. The authors conclude that accelerated rates of coral depletion can be expected considering the current CO2 emissions trajectory. The vital role coral reefs play within marine ecosystems may thus be increasingly compromised in the future.
There were two notable papers published in the last year that address direct links between global climate change and human impacts. Hsiang et al.  assert that the El Niño Southern Oscillation (ENSO) has driven civil conflicts in the past, particularly in regions that are so-called ENSO “teleconnected”. While the connection between climate and conflict has been anecdotally suggested in the past, this is the first quantitative demonstration of the link with conclusive results. They define their baseline control as the probability of new social conflicts arising during a La Niña event, and show that this doubles in teleconnected areas during an El Niño event. While this study cannot be generalized to include effects of gradual global climate change, it is an important step to understanding how changing environmental conditions can generate social conflict.
The second paper, by Curtis and Schneider , links dynamic population forecasts and climate change projections to estimate demographic shifts at the sub-national scale. They focus specifically on sea level rise in several coastal counties in the United States on a timespan of 5-30 years. The population of the sample area in 2000 was 12.5 million, with a projected 19.3 million affected by 2030. They find significant spatial variability of impacts on the countywide scale, and that impacts extend to external counties through changing migration streams. This variability may place a disproportionate burden on low-income households with reduced adaptive capacity. Additional studies using the same methodology would provide key information to development planners and governments in a changing global environment.
1. Pan, Y., et al., A Large and Persistent Carbon Sink in the World's Forests. Science, 2011. 333(6045): p. 988-993.
2. Xiao, Z. and C. Ximing, Climate change impacts on global agricultural land availability. Environmental Research Letters, 2011. 6(1): p. 014014.
3. Chen, I.-C., et al., Rapid Range Shifts of Species Associated with High Levels of Climate Warming. Science, 2011. 333(6045): p. 1024-1026.
4. Pandolfi, J.M., et al., Projecting Coral Reef Futures Under Global Warming and Ocean Acidification. Science, 2011. 333(6041): p. 418-422.
5. Hsiang, S.M., K.C. Meng, and M.A. Cane, Civil conflicts are associated with the global climate. Nature, 2011. 476(7361): p. 438-441.
6. Curtis, K. and A. Schneider, Understanding the demographic implications of climate change: estimates of localized population predictions under future scenarios of sea-level rise. Population & Environment, 2011. 33(1): p. 28-54.