Behavior and climate underpin spatial dynamics.
Urchin herbivores can bulldoze lush kelp forests into barrens that last decades. I showed that this happens primarily because urchins get too hungry to hide from storms, stress, and predators. Fitting dynamical models, we find that behavioral changes in per capita consumption explain spatial patterns much better than urchin density or environment across 201 reefs. Outbreaks of urchin grazing also span larger scales in California, explaining why forests, barrens, and catastrophic shifts between these states span large swaths of the coastline. Ecology Letters, 2021. bioRxiv preprint. Expanding these findings across the US West Coast using satellite kelp data, we are finding that modestly warmer climates are what triggers urchin outbreaks and forest collapse. bioRxiv preprint |
Local COVID-19 lockdowns outperform province-wide lockdowns. Developing and fitting province-wide epidemic models, we showed that slower epidemic growth in less densely populated areas and improved testing make flexible county-by-county restrictions feasible under daily commuting patterns. This reduces the number of worker days closed by 20% and fraction of counties closed by 50% compared with province-wide lockdowns, especially when closure criteria are coordinated regionally.
PNAS (Open Access), May 2020; lay summary |
The decline of an invader dominating the world's largest freshwater ecosystem. Highly invasive quagga and zebra mussels sometimes restructure entire food webs but in other cases nearly disappear after invasion. In the Great Lakes, quagga mussels now comprise c.a. 90% of all biomass. We quantify their food web impacts by fitting demographic models to mussel body size distributions. In resource-limited offshore habitats, models reveal a boom-and-bust dynamic: a huge initial cohort established high biomass, which now kills starvation-prone juveniles. Paradoxically, this means mussel consumption is now declining by ~35% while biomass continues to grow.
With Thomas Nalepa (University of Michigan), Alexander Karatayev, Lyubov Burlakova, Lars G. Rudstam (Cornell University). In Preparation. |