SYMP 5-1 - "Things fall apart": Why should ecologists care about trophic cascades in Yellowstone?

Tuesday, August 8, 2017: 8:00 AM
Portland Blrm 252, Oregon Convention Center
Andy Dobson, Ecology and Evolutionary Biology, Princeton University, Princeton, NJ

Chinua Achebe’s novel “Things Fall Apart” provided a very bleak vision for the future of African nations. It stimulated a generation of African leaders to govern their nations in ways that prevented things falling apart. Ecology faces similar problems. When things start to fall apart, we need to know how to put them back together again. This requires an understanding of how interactions between species can resonate through a food web and create trophic cascades. The reintroduction of wolves to Yellowstone National Park is widely celebrated as a conservation success story; it also provides a powerful example of why ecologists need to do more experiments at the ecosystem level. Elk populations have declined since wolf introduction, but buffalo numbers have increased; aspen, willow, and cottonwood recruitment has increased in some areas of the park, but not others. How important have wolves been in driving this trophic cascade, and might alternative factors such as long-term changes in precipitation produce similar effects?


While the rest of the symposium will focus on addressing different hypothesis for trophic changes in Yellowstone; I will make the case that we need to replicate the studies undertaken in Yellowstone in other parks in the US and throughout the World. Concomitantly, we need to develop models that provide better understanding of the consequences of species addition and loss to food web persistence and the conditions when this might lead to trophic cascades. Developing this understanding is a non-trivial scientific undertaking; ecological systems consist of many species of different sizes interacting non-linearly with each other at a diversity of different rates. Immunological and neurological systems have similar properties. This makes understanding the dynamics of complex biological systems much more challenging than comparable problems in the physical sciences. Understanding how ecological systems are assembled and preventing them falling apart is arguably the major scientific challenge of the 21st Century. We have a very short time horizon over which to address and understand these complex problems, another factor that sharply differentiates the ecological sciences from all other scientific enterprises. Insights gained from long-term monitoring and experimental studies in Yellowstone need to be combined with insights from similar studies in different areas and used to generate stronger theory and ecosystem level experiments that provide a deeper understanding of how ecological foodwebs and natural ecosystems function. Ultimately, ecologists need this knowledge to manage the natural environment in ways that prevent “Things falling apart”.