Allan Savory delivered a highly publicized talk at a “Technology, Entertainment, Design (TED)” conference in February of this year (2013) entitled “How to fight desertification and reverse climate change.” Here we address one of the most dramatic claims made – that a specialized grazing method alone can reverse the current trajectory of increasing atmospheric CO2 and climate change.
The talk was attended by many conferees and has since been viewed on the TED website over 1.6 million times. It has received substantial acclaim in social media, some of which is available at the Savory Institute website, but it has also received considerable criticism (of particular note is ablog post from Adam Merberg and an article in Slate magazine. Although these criticism quickly followed Mr. Savory’s presentation and are broadly supported by the available science, his sweeping claims have continued to resonate with lay audiences. An apparent example is his invitation to deliver a speech to Swiss Re during their 150 year anniversary celebration in London in September, in which he is quoted as saying “…only now due largely to my TED talk on the desertification aspect of the global problem, was the public becoming aware of such hope in a world so short on solutions…”.
As a result of the continuing discussion regarding this presentation, we felt compelled to interpret these claims within the context of Earth System science to facilitate broader discussions and evaluation. It is important to recognize that Mr. Savory’s grazing method, broadly known as holistic management, has been controversial for decades. A portion of this controversy and the lack of scientific support for the claims made for his method on livestock productivity and grassland ecosystem function may be found in peer-reviewed papers (e.g. Briske et al. 2008). This presentation, however, argued for an additional application to climate change.
We focus here on the most dramatic claim that Mr. Savory made regarding the reversal of climate change through holistic management of grasslands. The relevant quote (transcript by author from video provided on TED website) is as follows:
“…people who understand far more about carbon than I do calculate that for illustrative purposes, if we do what I’m showing you here, we can take enough carbon out of the atmosphere and safely store it in the grassland soils for thousands of years, and if we just do that on about half the world’s grasslands that I’ve shown you, we can take us back to pre-industrial levels while feeding people. I can think of almost nothing that offers more hope for our planet, for your children, for their children and all of humanity…”
While it is understandable to want to believe that such a dramatic outcome is possible, science tells us that this claim is simply not reasonable. The massive, ongoing additions of carbon to the atmosphere from human activity far exceed the carbon storage capacity of global grasslands.
Approximately 8 Petagrams (Pg; trillion kilograms) of carbon are added to the atmosphere every year from fossil fuel burning and cement production alone. This will increase in the future at a rate that depends largely on global use of fossil fuels. To put these emissions in perspective, the amount of carbon taken up by vegetation is about 2.6 Pg per year. To a very rough approximation then, the net carbon uptake by all of the planet’s vegetation would need to triple (assuming similar transfers to stable C pools like soil organic matter) just to offset current carbon emissions every year. However, the claim was not that holistic management would maintain current atmospheric CO2 levels, but that it would return the atmosphere to pre-industrial levels. Based on IPCC estimates, there are now approximately 240 more Petagrams (Pg) of carbon in the atmosphere than in pre-industrial times. To put this value in perspective, the amount of carbon in vegetation is currently estimated at around 450 Pg, most of that in the wood of trees. The amount of carbon that would need to be removed from the atmosphere and stabilized in soils, in addition to the amount required to compensate for ongoing emissions, to attain pre-industrial levels is equivalent to approximately one-half of the total carbon in all of Earth’s vegetation. Recall that annual uptake of carbon is about two orders of magnitude smaller than the total carbon amount stored in vegetation.
At a global scale, grasslands are generally distributed in regions of low precipitation across a wide range of temperatures, with precipitation particularly limiting grassland productivity. Within a zone, grassland carbon cycles respond significantly and sometimes dramatically to fluctuations in inter-annual precipitation. This is because soil water is essential for vegetation to remove carbon from the atmosphere in the process of photosynthesis and it also drives variation in microbial processes that affect the loss of carbon from soils. Consequently, soil water availability represents a much greater limitation to maximum carbon storage in global grasslands than does grazing management. Grasslands represent approximately 30-40% of the planet’s land surface and only a fraction of annual global productivity and carbon sequestration (~20% of global carbon stocks). It is simply unreasonable to expect that any management strategy, even if implemented on all of the planet’s grasslands, would yield such a tremendous increase in carbon sequestration.
Humanity faces many challenging problems in this period of human domination of planet known at the Anthropocene. These problems, including that of climate change, require efforts to find solutions in all sectors of society and that we engage in diverse and dynamic dialogue about potential solutions, including those that may lie far outside the current mainstream. However, potential solutions must be assessed with a dispassionate and rigorous treatment of risks, benefits, and costs. We should pursue solutions that are most likely to succeed on the basis of scientific validity and societal acceptance . Extravagant claims like those in Mr. Savory’s TED video must be weighed against known physical realities to credibly serve society.
Rangeland management strategies appropriately emphasize conservation of previously stored soil carbon, rather than sequestration of additional carbon, based in part on the limitations previously described. Emphasis should be placed on climate change adaptation, rather than mitigation as advocated by Mr. Savory, to support the well-being of millions of human inhabitants. Mr. Savory argues that we adopt his grazing method as a simple solution to resolve a key Anthropocene contributor – the ongoing perturbation of Earth’s carbon cycle. The appeal of this claim to casual observers is enhanced in that it does not require humans to face any tradeoffs. The implication is that we can continue to use fossil fuels and emit carbon into the atmosphere because application of holisitic management on the Earth’s grasslands provides a ‘silver bullet’ that will sustainably solve the climate change problem and provide abundant livestock products as well. We would be thrilled if a simple solution such as this existed. However, it clearly does not, and it is counter-productive to believe that it does. Humanity must look beyond hope and simple solutions if it is to successfully navigate its way through the Anthropocene.