The Conservation Cow

From carbonsoultionsglobal,com

Cows get a lot of bad press. Many people have heard that cows produce greenhouse gasses, including methane. According to a report in 2006 by the United Nations Food and Argiculture Organisation (FAO) our diets, and the meat in them release more carbon into the atmosphere than transportation or industry (Scientific American: The Greenhouse Hamburger, 2009). Methane is responsible for 20% of the warming created by long-lived green house gasses since pre-industrial times (Kirschke et al., 2013).

From autonomousmind.wordpress

Garnett (2009), and many other scientists, seem to agree that domestic livestock are a problem for both atmospheric carbon and valued ecosystems such as rainforest, which is cleared to make way for cattle ranches. In fact the post on Conservation by George Monbiot that I discussed in my last post, he mentions that domestic livestock are a major cause of global warming. He also points out that, in human-impacted systems, wild herbivores can be as well.

In part, I disagree with this view. I think that a change in how we use our livestock could turn them from an ecological nightmare to a key part of healthy ecosystem. A carbon source to a carbon sink. This has been suggested before, often in terms of altering their diets (For example, see Aquerre et al., 2011). But I think it needs to go further than that.

Wild herbivores can turn an ecosystem from a sink to a source of carbon in the presence of human interference. An example of this can be seen in the Serengeti. Pre-1960's, wildebeest numbers there fell from 1.2 million to 300,000 (Monbiot, 2014). The result echoed the hypothesised mechanism behind the loss of Australia's rainforest, which covered much of the country in Pleistocene times (Levy, 2011) (Monbiot, 2014). In the Serengeti, the decline in wildebeest caused dry vegetation to accumulate. This abundance of fuels resulted in wildfires, which burned around 80% of the Serengeti every year. Wildebeest numbers have since increased with conservation efforts, and now more vegetation is eaten, and their dung in incorporated into the soil. This represents a transformation of the Serengeti from a source of carbon to a sink. This shift is equivalent to the entire (current) emissions of carbon dioxide from burning of fossil fuels in the whole of east Africa (Monbiot, 2014).

In the US, cattle ranches occupy huge areas of arid land. They trample and munch up the strips of vegetation, collapse stream banks and drive out native animal populations. The deterioration of these habitats fueled a campaign to remove cattle from federal rangelands (Levy, 2011). Naturally the ranchers were unhappy. But was this the right thing to do?

This land has supported large herds of herbivores since long before the end of the Ice Age (Levy, 2011). These included native horse, camel and bison. The horse and camel went extinct in the end-Pleistocene, but the bison survived up until only a century before the conflict over the rangeland domestic cattle began (Levy, 2011). The bison numbered in the tens of millions. From 1830 to 1880, a deliberate effort to slaughter them reduced their numbers to only a few thousand (Knapp et al., 1999). At the same time, much of their habitat was ploughed up by farmers.

More recently, conservationists working on native prairie land began to experiment with introducing bison back into the mix. The study by Knapp et al. (1999) on bison ecology highlights the way the bison shape the landscape. Their faeces rich in nitrogen increases plant growth while their differential grazing (cattle are picky eaters) creates a diverse plant community (containing more species) in different stages of growth depending on when the bison were last there (Knapp et al., 1999).

From americanprairie.org
A bison herd on american prairie

This diversity increases the habitats available to the native wildlife, particularly the prairie birds (Knapp et al., 1999). For example, the lesser prairie chicken needs tall grass to hide its nest in, but short grass for its courtship displays (Levy, 2011). So bison play an important role in a diverse prairie ecosystem (Knapp et al., 1999). But they way they do so is through behaviours that they share with the domestic cow (Levy, 2011). So then, why do environmentalists dislike the domestic cow? And why are ranchers so afraid of the bison?

Cattle graze during spring and summer. In the autumn they are fenced into paddocks and fed hay. Bison on the other hand are free to roam and aren't supplemented in the winter months (Levy, 2011). The long-term study by Knapp et al. (1999) showed that when managed in the same sustainable way, both cows and bison increase the diversity of native prairie plants. The way the cow is used by people has a greater effect on its environmental impact than any behavioural or other traits (Knapp et al., 1999).

The best ranchers in the US find ways to keep their cattle on the move. In places like the UK, it's more difficult to imagine how this would be achieved, since we have very few large open spaces. Sadly, the open spaces remaining in the US are under threat from being sold to create suburban ranchettes, with far lower potential for sustainable use (Levy, 2011).

During the Pleistocene, grazers wandered wherever the fresh grass was, allowing the soil time to absorb the nutrients and the plants to grow. Dire wolves and other predators helped by creating a landscape where herbivores kept on the move and avoided certain areas out of fear (Levy, 2011). Domestic cows need to be moved by humans, requiring more effort than other methods. But the rewards are healthier grasslands, cattle and wildlife (Levy, 2011).