Bushmeat biogeochemistry: hunting tropical mammals alters ecosystem phosphorus budgets

The sixth R: Revitalizing the natural phosphorus pump

Phosphorus (P) is essential for all life on Earth and sustains food production. Yet, the easily accessible deposits of phosphate-rich rock, which underpin the green revolution are becoming rarer. Here we propose a mechanism to help alleviate the problem of "peak phosphorus". In the past, wild animals played a large role in returning P from ocean depths back to the continental interiors. In doing so, they collectively retained and redistributed P within the biosphere, supporting a more fertile planet. However, species extinctions and population reductions have reduced animal-mediated P transport >90% over the past 12,000 years. Recently a 5R strategy was developed to Realign P inputs, Reduce P losses, Recycle P in bio-resources, Recover P in wastes, and Redefine P in food systems. Here, we suggest a sixth R, to Revitalize the Natural Phosphorus Pump (RNPP). Countries are starting to mandate P recycling and we propose a P-trading scheme based on REDD+, where a country could partially achieve its recycling goals by restoring past animal-mediated P pathways. Accrued money from this scheme could be used to restore or conserve wild animal populations, while increasing natural P recycling.

A methodological roadmap to quantify animal-vectored spatial ecosystem subsidies

Energy, nutrients and organisms move over landscapes, connecting ecosystems across space and time. Meta-ecosystem theory investigates the emerging properties of local ecosystems coupled spatially by these movements of organisms and matter, by explicitly tracking exchanges of multiple substances across ecosystem borders. To date, meta-ecosystem research has focused mostly on abiotic flows-neglecting biotic nutrient flows. However, recent work has indicated animals act as spatial nutrient vectors when they transport nutrients across landscapes in the form of excreta, egesta and their own bodies. Partly due to its high level of abstraction, there are few empirical tests of meta-ecosystem theory. Furthermore, while animals may be viewed as important mediators of ecosystem functions, better integration of tools is needed to develop predictive insights of their relative roles and impacts on diverse ecosystems. We present a methodological roadmap that explains how to do such integration by discussing how to combine insights from movement, foraging and ecosystem ecology to develop a coherent understanding of animal-vectored nutrient transport on meta-ecosystems processes. We discuss how the slate of newly developed technologies and methods-tracking devices, mechanistic movement models, diet reconstruction techniques and remote sensing-that when integrated have the potential to advance the quantification of animal-vectored nutrient flows and increase the predictive power of meta-ecosystem theory. We demonstrate that by integrating novel and established tools of animal ecology, ecosystem ecology and remote sensing, we can begin to identify and quantify animal-mediated nutrient translocation by large animals. We also provide conceptual examples that show how our proposed integration of methodologies can help investigate ecosystem impacts of large animal movement. We conclude by describing practical advancements to understanding cross-ecosystem contributions of animals on the move. Understanding the mechanisms by which animals shape ecosystem dynamics is important for ongoing conservation, rewilding and restoration initiatives around the world, and for developing more accurate models of ecosystem nutrient budgets. Our roadmap will enable ecologists to better qualify and quantify animal-mediated nutrient translocation for animals on the move.