Scientists look at preventing 'tipping points' in agriculture

Growing food, fuel and fiber entails the use of fertilizer and irrigation systems and results in land-use changes. These ‘side effects’ of agriculture can lead to regime shifts or ‘tipping points’ which include desertification, salinisation, water degradation, and changes in climate due to altered water flows from land to atmosphere. But paradoxically, these very ecosystem services also hold the keys to ecosystem restoration.

So say researchers who will participate in a symposium titled “Tipping points in the biosphere: Agriculture, water, and resilience” during the Ecological Society of America’s Annual Meeting. The theme of the meeting is “Ecology-based restoration in a changing world” and some 4,000 scientists are expected to attend.

As human populations shift to more meat-heavy diets, trade of agricultural products increases, and as demand for biofuels grows the pressure on some agricultural systems is mounting. The challenge is to figure out how to meet these demands while at the same time keep the ecosystem functions that underpin productivity working.

Tipping points occur when an ecosystem is overwhelmed by the demands placed on it and can no longer function the way it did before. In other words, it loses its resiliency which ultimately can lead to land that is rendered useless for growing crops.

Elena Bennett (McGill University), organizer of the symposium, says that we need to better understand large scale regime shifts in order to develop policies that sustain, rather than degrade, the very systems upon which humanity depends.

One of the reasons current agricultural landscapes are so prone to regime shifts is that prevailing management of them has tended to focus exclusively on improving one type of ecosystem service (e.g. food production, fiber production, biofuels production) at the cost of others, explains Bennett:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: agriculture :: sustainability :: ecosystem :: climate change ::

She notes that agriculture is now one of the main driving forces of global environmental change. Bennett and other presenters in this session have identified potential tipping points related to water and agriculture that could have major global consequences.

No human activity has so large an impact on water systems as does agriculture, according to Johan Rockstrom (Stockholm Environment Institute, Sweden). He notes that the future will bring an even greater demand on fresh water for food production — by 2050 global water use for food production alone will need to double.

Line Gordon (Stockholm University, Sweden) will examine the redistribution of vapor flows brought about by irrigation. Gordon notes that the pattern of change varies and identifies the mid-United States, the Amazon, the Sahel, India, and Northern China as the most likely areas to undergo climate change, driven by these altered continental vapor flows.

Ellen Marie Douglas (University of Massachusetts) will focus on potential impacts on India’s Monsoon Belt, home to a large part of the globe’s population. India has the largest irrigated agricultural area in the world, with more than 90 percent of the country’s water supporting irrigated agriculture. Vapor fluxes in India’s wet season are up by 7 percent and are up 55 percent in the dry season. Douglas and her colleagues attribute two-thirds of this change to irrigated agriculture.

Drawing from research examples in the Mississippi River, Simon Donner (Princeton University), will discuss the role of nitrogen fertilizer in the health of downstream ecosystems, in particular their potential sensitivity to climate change.

Navin Ramankutty (McGill University) likens land use changes to fuel emissions in their potential to drive climatic changes. According to Ramankutty, local land cover changes may very likely generate changes elsewhere by altering the general circulation of the atmosphere. He points to Canada, Eastern Europe, the former Soviet Union, Mexico, and Central America as places where land clearing for cultivation may have inadvertently decreased suitability for growing crops.

Brandon Bestelmeyer (USDA-ARS Jornada Experimental Range) will examine tipping points in rangelands and will explore various socio-economic factors contributing to rangeland degradation.

Others presenting at the session are Garry Peterson (McGill University), Lance Gunderson (Emory University), and Max Rietkerk (Utrecht University, The Netherlands).

“Our hope is that if we can identify potential regime shifts, we can alter our management to avoid them,” says session organizer Bennett.

Picture: 'terra preta' or 'dark earth' soils offer an example of an agricultural system that withstands the test of time. The technique is based on sequestring biochar (agrichar) in soils to make them more fertile, to improve their water retention capacities and to boost agricultural output in a genuinely sustainable way. Left: a nutrient poor oxisol, right: a biochar-enriched, fertile oxisol. These soils are now being looked at in the context of carbon-negative biofuels, which could help restore degraded soils. Courtesy: Bruno Glaser.

References:
Eurekalert: Tipping points - August 6, 2007.