What place for livestock on a re-greening earth?

Humanity is quickly encroaching upon the finite limits of the biosphere. As our numbers and appetites grow, food supplies become less secure, reserves of clean energy dwindle, pools of freshwater evaporate, the atmosphereʹs capacity to absorb our emissions diminishes and space for human and biotic habitat grows scarce. In response, some are now asking whether the biosphere can support our growing herds of domesticated livestock, notably ruminants. My aim in this review is to contemplate the place of these animals in a world in need of re-greening, in more ways than one. In addressing this objective, I advance the premise that the place of livestock is examined best from the vantage of ‘land’, broadly defined. Livestock have been implicated in many injurious processes: land use change, excess water use, nutrient excretion, fossil energy use, competition for food and emission of greenhouse gases. At the same time, they offer numerous benefits: producing food from human inedible sources, preserving ecosystem services, promoting perennials on croplands, recycling plant nutrients and providing social benefits. Thus livestock can be both stressors and benefactors to land and the aim of researchers should be to shift the net effect from stress to beneficence. To advance this goal, I offer seven questions, seen through the lenses of ‘systems’, ‘place’, ‘time’ and ‘community’, mostly to foster discourse. How do we better study whole systems? How do we better tune the systems to local land? How can we know long term consequences? How do we measure progress? How do we choose among trade-offs? How do we engage society? What will (or should) our successors’ livestock systems look like? Humans and their livestock are intertwined to such an extent that their symbiosis will not likely soon be severed. Livestock offer many benefits to human society and often their place in ecosystems can be ecologically justified. But that does not mean that all ways of raising them are beneficial, nor that they necessarily fit everywhere. In coming decades, researchers, in concert with practitioners, consumers and policymakers, will need to show creativity, foresight and courage to envision new ways of melding animals into our ecosystems, not only to minimize harm, but to advance their re-greening. aper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.