Functional Collapse: Reconstructing animal-vectored nutrient fluxes in paleoenvironments

Centuries of human activity has led to declines in species’ ranges and abundances, but relatively little is know about the ecological functions of many species before human arrivals. One such function is  animal-vectored nutrient fluxes – that is, the cross-ecosystem movement of nutrients by animals – which can have significant impacts on the recipient communites, such as increased primary productivity, biodiversity and ecological resilience. We developed a framework to reconstruct paleo-nutrient fluxes, using seabirds in Aotearoa New Zealand as a case study. Aotearoa New Zealand is the ‘seabird capital of the world’, hosting ~25% of the worlds seabird diversity, and ~10% being endemic breeders. It is also one of the last land masses to be settled, with humans only arriving ~800 years ago. The last ~200 years though, have brought about the most significant changes, with widespread land use change, the introduction of numerous mammalian predators and numerous avian extinctions and extirpations. Through a synthesis ecological niche modelling, allometric relationships and computational simulations we show that burrowing procellariiform have been extirpated from former breeding colonies, and that nutrients fluxes have collapsed to less than 20% of their former volume, and are recieved by less than 10% of the former area. We estimate that the primary collapse occurred within ~50 years of the introduction of mammals, and would continue today without active management of introduced predators. By reconstructing where and how nutrient fluxes have been lost, we can better understand the consequences of human actions and how ecosystems function can be restored.
André is currently a Post-doctoral Scholar at The Ohio State University in the Department of Evolution Ecology and Organismal Biology, but conducted the research presentedat the University of Auckland, School of Environment. His research primarily focusses on ecosystem level changes over the last 21,000 years, and how data can best be leveraged to gain robust insights into community assembly and ecosystem functions.