"Planetary boundaries, even if roughly quantified, represent a scientifically justified sustainability goal," Helena Kahiluoto told environmentalresearchweb. "But only the spatial disparity in the history of human actions that led to crossing the critical boundaries reveals the distribution of the responsibility to pull back."
According to Kahiluoto, whilst this is also true of climate change, it’s particularly relevant for nutrient use because it determines access to food. Historically, nutrient use has contributed not only to the current disparity in wealth and development, but also to the reserves available for reuse.
"We wanted to show an example of the critical social boundary of equity that delineates the safe space for humanity, also manifested by the conflicts that led to the current migration to Europe," she said. "The remedies need to build on this insight."
The accumulated nutrient use per capita globally is 2300 kg of reactive nitrogen and 200 kg of phosphorus. The figures for Finland are 3400 kg of reactive nitrogen and 690 kg of phosphorus; for Ethiopia the accumulated nutrient use per capita is 26 kg nitrogen and 12 kg phosphorus. Finland exceeds its critical nitrogen boundary by 40 kg per head per year and the accumulated excess is 65 kg per head per year. Although, globally the current excess for reactive nitrogen is 24 kg per head per year, Ethiopia could increase its accumulated flow of the nutrient.
When it comes to phosphorus, both Finland and Ethiopia exceed their critical boundary. In Finland, this is because there has been too much use of phosphorus to produce food in the past. In Ethiopia, in contrast, it’s because producing food has removed too much phosphorus from the system due to lack of input and inadequate waste management.
"The disparity in historical access to nutrients rather than in the boundaries set by the local ecosystems is decisive for the excess, and thus for the remedies," said Kahiluoto. "Two ecological tipping points can be identified, both ones already exceeded: the tipping point of the dominance of internal loading [redistribution from sediment] in expanding areas of lakes, coastal water systems and estuaries of the industrialized world, and the tipping point of soil degradation in lack of nutrient replenishment in large areas of the developing world."
As a consequence, according to the researcher, the pivotal social tipping point of food security is repeatedly exceeded in the developing world. "For example in Ethiopia, there are millions of people under acute threat of dying from hunger just now, due to the harvest lost by delayed rains and the reduced water retention capacity of degraded soil," she said. "We demonstrate that there is synergy obtainable between reversing the system state to the safe side of the tipping points, and more generally between returning to the safe space ecologically and socially. This means synergy between benefits to rich and poor countries."
There are many frontiers on which to proceed. "There are knowledge gaps related to the ecological, technological and institutional challenges in utilizing the nutrient reserves in residues, field soils and water sediments, and in recycling nutrients including micronutrients and carbon from the industrialized world to restore degraded soils of food-insecure regions," said Kahiluoto. "The global institutional framework to finance such recycling, and the barriers and tools for the sustainability transition, need to be identified." What’s more, reaching a circular and just global nutrient economy will require an interdisciplinary approach and team, the researcher believes.
Kahiluoto and colleagues reported their findings in Environmental Research Letters (ERL).
Related links
- Local and social facets of planetary boundaries: right to nutrients Helena Kahiluoto et al 2015 Environ. Res. Lett. 10 104013
- ERL
- Helena Kahiluoto