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research newsiiasa research www.iiasa.ac.at 5 summer 2017 ◼ options IIASA at EGU Over 20 IIASA researchers participated in this year’s European Geosciences Union General Assembly, one of the largest international research conferences focused on Earth sciences. IIASA scientists from five of the institute’s nine research programs presented new work at the meeting, which takes place in Vienna every spring. www.iiasa.ac.at/events/egu-17 Win-wins on climate and food Efforts to reduce greenhouse gas emissions from the agriculture and forestry sectors could lead to increased food prices. In a new study presented at EGU, IIASA researcher Stefan Frank found several strategies that could help mitigate climate change while avoiding steep hikes in food prices. In particular, the study found that reducing deforestation and increasing soil carbon sequestration through agricultural practices could significantly reduce greenhouse gas emissions without jeopardizing food security. Citizen science for disaster response At EGU, researchers launched a test run for a new citizen science campaign that links volunteers around the world with a way to help communities after major disasters. The campaign relies on the IIASA-developed app Picture Pile, which asks users to compare sets of before and after images to identify damage to buildings. During the test phase, the campaign is sorting through data from Hurricane Matthew, which devastated Haiti in 2016. www.iiasa.ac.at/news/crowd4sat-17 Ancient groundwater A new study presented at EGU, and published in the journal Nature Geoscience, found that fossil groundwater makes up a significantly higher proportion of the Earth’s groundwater than previously thought. It also found that this ancient water—which has been stored underground for over 12,000 years—is not immune to modern contamination, as had been widely assumed. Groundwater used for irrigation is particularly worrying, since it is often untested before being applied to crops, says IIASA Water Program Deputy Director Yoshihide Wada, who contributed to the study. www.iiasa.ac.at/news/fossil-water-17 T raditional ecological theory holds that each species on this planet occupies its own niche, or environment, where it can uniquely thrive. But forests, especially tropical forests, are home to thousands of species of trees—sometimes tens to hundreds of tree species in the same forest—a level of biodiversity ecologists have struggled to explain. In particular, ecological models have been unable to account for the unexpectedly large number of varieties of shade-tolerant tropical trees and shrubs, which appear to occupy the same niche and yet coexist. This raises the fundamental question: are separate niches really always needed for species coexistence? In a recent study, IIASA Evolution and Ecology Program Director Ulf Dieckmann and colleagues provide a new model that elucidates the ecological and evolutionary mechanisms underlying these natural patterns. The researchers combined tree physiology, ecology, and evolution to construct a new model in which tree species and their niches coevolve in mutual dependence. While previous models had not been able to predict a high biodiversity of shade-tolerant species to coexist over long periods of time, the new model demonstrates how physiological differences and competition for light naturally lead to a large number of species, just as in nature. At the same time, the new model shows that fast-growing shade-intolerant tree species evolve to occupy narrow and well-separated niches, whereas slow-growing shade-tolerant tree species have evolved to occupy a very broad niche that offers enough room for a whole continuum of different species to coexist—again, just as observed in nature. Until now, a different framework—called neutral theory—had to be invoked for explaining tropical tree diversity. “Our model shows how neutral theory follows from niche theory,” Dieckmann says. “We hope this work will result in a better understanding of human impacts on forests, including timber extraction, fire control, habitat fragmentation, and climate change.” KL Further info Falster DS, Brännström A, Westoby M, & Dieckmann U (2017). Multitrait successional forest dynamics enable diverse competitive coexistence. Proceedings of the National Academy of Sciences 114 (13): 2719-2728. [pure.iiasa.ac.at/14354] §  www.iiasa.ac.at/news/forest-17 Ulf Dieckmann dieckmann@iiasa.ac.at How nature creates forest diversity Time since disturbance (yr) The new model allows researchers to predict how natural variation of forest structure depends on environmental conditions. When the model is run for different environmental conditions, it returns results that mirror the variation observed in natural environments.