Background before questions and before methods

Before I delve into the exciting journey of selecting and carrying out some data collection methods, I thought it would be helpful to start with some background to explain why I do the research I do.

Why phosphorus?


P is an essential resource for all living things (from plants to humans) and it is not substitutable.  Human management of P resources has become problematic. Unlike “natural” ecosystems, which recycle the majority of their P, humans use P in a one-way flow from mines to the ocean.

The major use for P is in agricultural production, which if fine in itself as plants need P, but along each step of the food chain we incur significant losses.

The problem with P management in our food system double sided: it is in limited supply but there is also too much P is some places. We need concentrated P to apply as fertilizer. We mine high-P deposits to make fertilizers, but these high-grade mined reserves are finite and they are also geopolitically concentrated. We are thus faced with both physical and economic scarcity of a non-substitutable resource that is key to food security. On the other hand, looses of P from mining, from agricultural fields, from food processing, and from wastewater treatment plants can accumulate in water bodies downstream.  Such a high concentration of nutrients in a water body allows for algal blooms, which can be toxic, and can lead to hypoxic zones (too little oxygen) where nothing can live.

We can change the way we manage P though. We can decrease our use of non-renewable P and decrease pollution by increasing efficiency and recycling through the food system. There is great research going on around the world in many fields to make P management more sustainable.  There are a few networks of scientists, practitioners, and decision-makers trying to bring some of these research efforts together including the Sustainable Phosphorus Initiative based at Arizona State University, Global P Research Initiative from University Technology Sydney in Australia and other partners, the Dutch Nutrient Platform, and Global TraPs from Zurich, Switzerland.

Why cities?

Cities are a key step in the movement of P across the global food landscape. They concentrate the demand for food and thus P. Cities also concentrate the production of high P waste, through the waste of food but also human waste (we excrete 98% of the P we eat), contributing to pollution downstream. I think there is great potential for cities to recycle their high-P waste, thus contributing to urban food security by decreasing dependence (and price fluctuations) on mined-P resources.  Urban and peri-urban agriculture (info here) may play a role in more sustainable urban P management, along with other practices and behaviors, but we need more information.

In order to improve how we manage P we need to look at how humans and ecosystems have cycled P in the past and how P is cycled today, in addition to thinking about the future. P management is complex because it is linked to the management of many other resources (including nitrogen, carbon, water, and land just to name a few).  P management is also complex because we must look at the global picture while considering local variability which arises from different ecological and social contexts and different needs. It’s simply fascinating! Next I will try and delve in to what I mean when I say I am working on “sustainable phosphorus management”.


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