Spotlight on the overlooked role of horses as carbon sequesters

A band of Kiger mustangs on the range. The Kiger mustang is a strain of mustang horse located in the southeastern part of the U.S. state of Oregon.
A band of Kiger mustangs on the range. The Kiger mustang is a strain of mustang horse located in the southeastern part of the U.S. state of Oregon. © Craig C. Downer

Horses and burros, including especially wild, naturally living ones, play a major role in combatting global warming and do this in a variety of ways. One of these concerns their superior ability to sequester, or “lock away”, carbon.

They remove carbon from the atmosphere, where, in the form of carbon dioxide, methane and other heat-trapping gases, this element accelerates a dangerous, oven-like increase in temperatures on the entire planet Earth.

Related: Wildlife specialist adds voice to plight of Onaqui mustangs

All members of the horse family Equidae, as well as their Mammalian Order Perissodactyla, play this same vital and life-saving role. This includes also the various onagers, zebras, tapirs and rhinoceroses of the world, nearly all of which are listed as threatened or endangered with extinction in the Red List put out by the World Conservation Union’s (IUCN) Species Survival Commission (2021). As a member of the IUCN SSC, I have written action plans and species resumes to mount a global effort to save and restore these very important species together with their appropriate habitats.

Much of the superior ability of the horses and burros to sequester carbon is related to their special digestive system. This is different from the ruminant digestive system of many other plant-eaters, or herbivores, in our world. These include many millions of cattle, sheep, goats, deer, elk, etc, that are forced in excessive numbers onto ecosystems the world over, including in the United States.

Horses and burros possess a monogastric, cecal-fermenting digestive system that is less complex than that of the multi-stomach, rumen-fermenting digestive system of ruminant herbivores. As a consequence, these equids do not as thoroughly decompose their food as do ruminants. As a consequence, the chemistry of equid droppings is more organically intact and complex. This fact has enormously positive consequences for habitats. One of the chief advantages is that equine feces contribute to more vital soils by augmenting their humus content. As many gardeners know, humus is crucial to healthy soils, making these more nutrient-rich and water-retaining. Indeed, the renowned San Francisco Botanical Garden has soils that were enriched from sandy beach loam by mixing horse manure back in the 1870s, and horse droppings continue to play a major part in keeping this garden so exuberant today.

The health of ecosystems depends upon healthy plant life, which depends upon healthy soils. Horses create more robust soils that cause grasses, forbs, bushes and trees to flourish when adequate water, healthy air and sunshine are added into the mixture. In regions where they belong, horses have been proven to allow a much greater diversity of species of both plants and animals together with their interrelated roles in the living community. This gives greater resistance and resilience to horse-containing ecosystems. This has been proven here in North America and in many places all over the world. One prime example concerns the restoration of Spanish Retuerta horses in overgrazed ecosystems in Andalusia. This ongoing program is restoring ecosystems that had been overgrazed by livestock for centuries and quite quickly. All the while this program is preserving a rare and ancient horse lineage.

Other examples include the Siberian tundra-restoration project involving the hearty Yakutian horses, along with Saiga antelope and Musk oxen (see Zimov, 2005), the restoration of sheep-overgrazed grasslands in Argentina by reintroducing Pampas wild horses, and similar restoration projects in England, Romania, Poland, France, Africa, and other ecosystems throughout the world. Both the resistance and the resilience of such ecosystems are crucially important today for the survival of life on Earth. The horse is considered by leading ecologists to be an ideal restorer of degraded and even poisoned ecosystems in many places throughout the world where they also help combat global warming through carbon sequestration and other means such as prevention of catastrophic wildfires (see Naundrup and Svenning, 2015 in the references below).

Yakutian horses in winter.
Yakutian horses in winter. © Унаров Максим Владимирович CC BY-SA via Wikimedia Commons

Horses can be better carbon sequesters than cattle, sheep and other ruminants because when horses “go to the bathroom”, or defecate, their feces are often covered over by sediments, such as mountain erosion. Through this burial, the more intact carbon-containing molecules contained in their feces are sealed off from air and its oxygen. When conditions permit them to remain thus for long periods of time, they remain unoxidized and undecomposed, such as in the peat bogs of colder northern lands such as Russia, Scandinavia, Eurasia and Scotland. Consequently, large amounts of carbon can be removed from the atmosphere which results in less solar radiation being absorbed, which counters the oven-like Greenhouse Effect that is putting all precious life on Earth in such great danger today!.

And regardless of whether they are buried or not, their feces still “lock up” carbon for much longer than do the feces of the ruminant herbivores, since they take longer to be decomposed. And this is a very healthy factor for ecosystems that lends them more long-term security and stability.

I must also stress how very much more heat-trapping and carbon-containing gases are emitted by ruminant digesters such as cattle and sheep, certain members of the deer family, etc. These cud-chewing, multi-stomach, pre-gastric-digesting and rumen-possessing herbivores emit much more methane gas (CH4) than the horses and other equids do. And methane is many times more heat-trapping in regard to solar radiation than carbon dioxide, although it dissipates more rapidly. Still, it lingers for many years and, quite frankly, we earthlings simply do not have the time left in which to accomplish the reversal of this very insidious, pervasive and inimical process known as Global Warming, or Global Heating, or Global Climate Change. (See What Are the Primary Heat-Absorbing Gases in the Atmosphere?.)

Another important point concerning catastrophic fire prevention by horses. Because of their wide-roaming lifestyle and ability to handle coarser, drier vegetation and to convert this into richer more moisture-retaining soils, they are the ideal species in many areas to prevent such destructive acts of nature. Also, it should be borne in mind that the prevalent “cow pies” or droppings of cattle are easily ignited, for example, bursting into flame when struck by lightning due to their extreme dryness. Many examples exist of major fires having been initiated in the abundant cow pies sparked by many fire sources, including campfires, overheated catalytic converters or even iron horseshoes struck on hard rocks.

There should be many more naturally living horses and burros in America as well as in many places throughout the world. The western United States has become an area of extreme wildfires and this situation is predicted to intensify as temperatures rise in future years. Furthermore, there is a sore lack of large herbivores to fulfil vital ecological roles both in North America and throughout the world, because of the die-out of many such species after the last Ice Age some 12,000 years ago. These both could and should be replaced judiciously with a balanced natural cast of species within the ecosystem (see Pires et al, 2017; Ripple, 2015, Odadi et al, 2011, in references below).

Consequently, there is a concomitant desperate need to reduce the hordes of methane-releasing cattle and sheep and other ruminants where they are being foisted in unnatural and unbalanced numbers. Here they strip the forage, guzzle enormous quantities of its water used in digestion and trample soils and vegetation, often along riparian habitats such as streams, lakes and springs, where European-derived cattle are especially drawn. Therefore, it becomes obvious that what the world needs now is many more wild horses and their kin to fulfil their life-saving and life-restoring roles.

There should be many more naturally living horses and burros in America as well as in many places throughout the world.
There should be many more naturally living horses and burros in America as well as in many places throughout the world, writes Craig Downer. Image by Steppinstars

Horses, burros and their kin play a superb role as “Johnny Appleseeds” within the natural world where they evolved and in some places still inhabit today. Other members of the horse family Equidae, such as zebras and onagers, as well as members of the tapir family: Tapiridae and rhinoceros family: Rhinocerontidae (all in the order Perissodactyla) are likewise famous intact seed dispersers (see Downer, 2001). Again, this involves the fact that their post-gastric, cecal fermenting digestion does not as thoroughly degrade the forage, including seeds, that they consume. A very important consequence of this is that many of the seeds they eat are deposited in the fertile beds of their droppings where they germinate, sprout and grow to become mature flowering plants that support many other species and embellish our shared life home.

Because of their more intact chemistry, horse droppings decompose more slowly to provide a more long-lasting fertile soil bed in which many diverse seeds can germinate. This has been proven throughout the world: We must not turn a blind eye to this great ecological service.

When we add in all the many insects, including pollinators, birds, mammals, reptiles and even amphibians and fish that benefit from these plants, it is plain to see how very important horses and their kin are in the world of nature, which they greatly enhance, bolster and even embellish. And remember that the greater chemical complexity of the equine droppings is key to understanding and supporting their major role as carbon sequesters and global warming combaters that is so crucial today.

» Article courtesy Love Wild Horses, whose Wildfire-Wild Equine-Global Warming Protection plan aims to protect both horses/burros and ecosystems both on public and private lands. These wild horses and burros have lost their rightful place on the public lands and are in desperate need of healthy, safe areas where they can do a world of good as indicated above. This will save them from further dispiriting incarceration, suffering and death including their frequent sale to slaughter.

Please help Love Wild Horses rewild wherever it is possible, because these horses deserve a chance — and the planet deserves their crucial help in preserving and restoring healthy, balanced and well-functioning life communities that are so desperately needed today.

Craig Downer at Uluru in Australia's Northern Territory.
Craig Downer at Uluru in Australia’s Northern Territory. © Mae Lee Sun

A pioneer-descended Nevadan, as a boy Craig Downer fell in love with the natural world, oft while riding his best friend Poco. This passion led him to pursue a career in wildlife ecology and to earn an A.B. in Biology with specialization in Ecology from the University of California-Berkeley, an M.S. from the University of Nevada-Reno, and to attain Ph.D. candidature at Durham University in Britain. His studies and observations of wild horses led him to work with Wild Horse Annie in insisting that the true intent of the Wild Free-Roaming Horses and Burros Act be implemented throughout America. He served as a Peace Corps wildlife ecologist in Colombia and is the first biologist to have successfully captured, radio-collared and tracked the endangered Mountain, or Andean, Tapir as part of his doctorate studies, His organization, the Andean Tapir Fund, continues to successfully defend and protect this dwindling species, along with its diminishing cloud forest and paramo habitats. The Andean Tapir Fund has now adopted within its mandate “preserving and restoring all of the Perissodactyls in and together with their natural habitats including all species within the Horse, Tapir and Rhino families.” Craig is a member of the IUCN Species Survival Commission and his organization works to save all members of the Horse, Tapir and Rhino families (Order Perissodactyla) in their natural habitats. Visit Craig’s website.


Anonymous. 2019 (July 31). What is the carbon footprint of a horse compared to an automobile?

Bell, R.H.V. 1970. The use of the herb layer by grazing ungulates in the Serengeti. IN: Animal Populations in Relation to their Food Source. British Ecological Society Symposium. Ed. Adam Watson. Oxford, U.K. Blackwell Science Publications.

Downer, Craig C. 2014. The horse and burro as positively contributing returned natives in North America American Journal of Life Sciences. 2014; 2(1): 5-23.

Downer, Craig C. 2014. The Wild Horse Conspiracy. EBook or printed edition with photo illustrations and bibliography. 313 pages.

Downer, Craig C. 2001. Observations on the diet and habitat of the mountain tapir (Tapirus pinchaque). Journal of Zoology (London). Vol. 254: 279-291.

Dwilson, Stephanie Dube. 2017 (Sept. 21). How to Garden with Horse Manure.

ELCR. 2014 (July 23). Ecological Benefits of Horses.

Equine Nutrition Nerd.

Follett, R.F. and D.A. Reed. 2010. Soil Carbon sequestration in grazing lands: societal benefits and policy implications. Rangeland Ecology and Management 63(1): 4-15.

Hackmann, timothy, M.S. 2008 (Dec.) Studies of Ruminant Digestion, Ecology, and Evolution. M.S. Thesis. University of Missouri.

Helmer, Jeroen. The wild horse — a keystone species. Arc Nature www.ark.en/paard. A color graph showing benefits of ecological relations of horses.

Janis, Christine, Ph.D. 1976 (Dec.). The evolutionary strategy of the Equidae and the Origin of Rumen and Cecal Digestion. Evolution 30: 757-774.

Marcus, Claus. 2013 (March 2). Digestive physiology and feeding behaviour of equids – a comparative approach. Horse health Nutrition. European Equine Health Nutrition Congress. Gent, Belgium. March 1-2, 2013. Pages 25-33.

Naundrup, P. J., and J. C. Svenning. 2015. A Geographic Assessment of the Global Scope for Rewilding with Wild-Living Horses (Equus ferus).

Odadi, W. et al. 2011. Facilitation between Bovids and Equids in an African Savanna. Evol. Ecol. Res. Vol 13: 237-252.

Pires, Mathias. et al. 2017. Pleistocene megafaunal extinctions and the functional loss of long-distance seed-dispersal services. Ecography Vol. 41. 10.1111/ecog.03163.

Ripple, William J. et al. 2015 (May 1). Collapse of the World’s largest Herbivores. Science Advances. Volume 1, No. 4.

Rutgers University.

Zimov, S.A. 2005. Pleistocene park: return of the mammoths’ ecosystem. Science 308: 796-798.

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16 thoughts on “Spotlight on the overlooked role of horses as carbon sequesters

  • July 17, 2021 at 6:01 pm

    Thanks so much for publishing my article for which I had support from Love Wild Horses. It is so important that we humans come to more fully recognize all the many marvelous contributions that horses and their kin make to ecosystems and how they can act as natural healers and balancers in so many places today, filling roles that are essential to the well-functioning of not only the local but the global ecosystem.

    • August 9, 2021 at 3:25 pm

      Failure to identify the Wild horse and burro as a Cultural Resource has extinguished many distinct population segments of Native North American Herds. It is the duty of the Advisory Council on Historic Preservation (ACHP) to correct this fatal flaw and provide for the amendment of Resource Management plans

      The First Americans, Their Customs, Art, History and How They Lived
      Chief Consultant Stanley Fried PH.d. ,
      Curator Dept of Anthropology: The American Museum of Natural History

      Brief Summary of multiple tribal horse cultural references:
      The Southwest Indians were the first of all tribes to own horses. They initially tended those of the Spaniards and Europeans, and inevitably came to own and selectively manage their own herds. Being responsible for the horses’ care, Tribal women’s lives were also radically altered as her bridal value was calculated on the number of horses her suitor gave her father .
      By 1770 nearly every grassland tribe was well supplied with mounts and became peerless riders and breeders. To the white man coming onto the Plains, these pintos, duns, and splotched cayuses appeared no match for their own heavy grain-fed mounts, yet in battle or on the hunt the Indian’s horses far excelled those of the Europeans.
      The evolution of the wild horse and burro today has resulted in herds of distinct population segments that have been subjected and adapted to the harshest of environments and predators. But can they survive the biggest threat of all…a government with an extinguishment agenda of America’s Protected Icon?

    • August 30, 2021 at 2:51 am

      By all means, these beautiful indigenous creatures must be protected and respected.
      I am curious, if perhaps the wild mustangs could Alannabe and should be considered a “keystone” species? If so, that alone may bolster protection efforts.

  • July 19, 2021 at 9:30 am

    We used horse manure on our garden because we have so much of it around. We grew very lovely weeds. Horses spread weeds very well because of their digestive system. In areas such as the Bogong High Plains of Victoria (Aus) there is a problem with weeds introduced by cattlemen and others. One of the most invasive weeds is Hawkweed and it has the potential to make useless vast amounts of grazing land. It has been found in an area used for cattle but also close to a ‘horse camp’. There is also a population of feral horses close by. The natural environment has developed over many thousands of years and people like Craig Downer believe introduced feral horses should be allowed to stay. He champions their cause with suspect information or information cherry picked to suit his agenda. I understand he likes horses but he seems to care very little for the actual damage they do to the environment which far out ways any perceived benefit they provide.

  • July 21, 2021 at 6:33 am

    Horses can spread native species as well and their improving the soil can also benefit native species, depending on what is available for them to eat. It is wrong to just lay the blame on the horses for changes that we people have introduced into the ecosystem. Also the prejudiced term “weed” is often very unjust, since many of these plants are responding to the conditions that people have created in our shared life home. We should be thankful in many cases that there are some species at least who can still manage to heal the wounds that humanity has caused. Also these hardy pioneer plants often pave the way for the restoration of the original ecosystem, or one very similar to the original and that functions well, after natural succession is allowed to occur, or run its course. My detractor accuses me of “cherry picking” to defend the horse’s place in our world. Well, to this I would reply that the detractors of the naturally living horses really go to extremes when it comes to “grinding their axe” against the naturally living horses, because they ignore so much concerning their positive contributions including catastrophic wildfire mitigation and even prevention, that is so vitally important today!

    • August 26, 2021 at 6:04 pm

      Get rid of the blm give the land back to the Indians get rid of the cows save the wild horses lock the cows up poor horses what there doing is cruelty to animals basterds

  • July 21, 2021 at 5:55 pm

    The negative impact of global warming is quickly becoming more and more apparent. As reported by the National Climate Assessment, the number one cause of global warming is due to human influences, particularly carbon pollution. This article by Craig Downer focuses on how wild horses and burros can help counter carbon pollution with their “superior ability to sequester carbon” because of their special digestive system. It’s time to try to heal our earth and the damage done by mankind. Wild horses and burros can certainly help.

    A comment by an anti wild horse person states his opinion that the horses damage the environment more than they benefit it. It seems to me this person has “cherry picked information to suit his own agenda”. For instance he blames the wild horses for spreading plants that were “introduced by cattlemen and others”. Yet he blames not the cattlemen for having introduced the plants he refers to as weeds. He also says, “We used horse manure on our garden because we have so much of it around. We grew very lovely weeds.” Why did he use the manure in his garden if he knew it would grow plants that he didn’t want and then turn it around and blame it on the horses?

    Global warming is already happening. Wild horses can help counter it. To discard the benefits of wild horses because of a fear that wild horses may or may not spread certain plants that were introduced by cattlemen has no scientific merit.

    • September 25, 2021 at 8:21 am

      Thanks so much, Rusty! So good to know there are others who see the light! It is imperative that people become much more enlightened on this subject and let the amazing horses play their life-restoring role today. They have been here for millions of years and know what they are doing! We must just let them! Release them where they are most needed and know how to live and to restore the life community.

  • July 23, 2021 at 3:50 am

    This suggests a reason that isolated tribes such as Cossacks have survived so long with seemingly few diseases and rare decimation.

  • July 25, 2021 at 11:29 am

    Thanks so much for these supportive and intriguing, insight expanding comments, Sandra and Rusty.

  • August 3, 2021 at 8:09 pm

    This article should be shared with the Bureau of Land Management who is on an unnecessary and cruel wild horse roundup spree this summer as they are removing 6000 wild horses which they say is due to the drought, yet they have no problem with the millions of sheep and cattle destroying the landscape and drinking up all the water. Their roundups have always been based on lies to keep the ranching industry happy, and this huge roundup this summer shows just how determined they are to eventually make the horses extinct in the wild.

    • August 5, 2021 at 6:27 pm

      Yes I read about the additional 6000 that they announced they are planning on rounding up. They use any excuse to eliminate them from their rightful habitat all the while giving nearly all the forage and water to other interests like livestock, mining or energy operations. They are shameless in their violation of their noble duty to defend the rights and the well being of the naturally living horses and burros and their legal habitats. These do a world of good for the life community including combatting Global Warming. See my book

  • August 30, 2021 at 3:35 pm

    I used to work at the prison and know the guy they runs the AZ Wildhorse program that you are bashing. If something isn’t done to help save these wild horses, they not only starve to death but they breed too much and become over populated and have numerous health issues. Furthermore, the Wildhorse program helps the inmates build their self esteem, it saves the horses, and it allows these horses to be adopted out to anyone or any agency that wants to purchase them. It’s a win-win. I’m willing to bet you know absolutely nothing about this program but you ought to look into it….

  • September 4, 2021 at 7:50 am

    What you say is not true, Doxie. I do know about this program. I have nothing against this program, but I think your reaction is not called for. My message is about the value of the wild horses and burros and other Perissodactyls in the world of nature and how they can help counter the life-threatening effects of Global Warming. What you say about the starving horses being overpopulated is not true. They are actually underpopulated but are being subject to a very unjust squeeze play, set up by hostile people who have targeted them and then issue shallow, dishonest excuses for their cruel and dishonest policies. You should read my other article

  • September 25, 2021 at 8:24 am

    The horses and burros restore soils, disperse intact germinable seeds, open up thickets and do not release the enormous quantities of heat-trapping gasses that
    the domestic ruminants like cattle do and which is greatly exacerbating global warming and threatening the future of life on Earth, just as are fossil fuel combustions!

  • May 1, 2023 at 10:52 am

    Another very important point that I was reminded of at the recent save our wild horses conference in washington dc (where I also gave a powerpoint presentation) concerns the following: since horses are great promoters of grass-dominated ecosystems they are likewise of their vast and intricate and voluminous root masses. And it has been proven that these lock away beneath the soil survice an amazing amount of carbon in the organic molecules involved with the roots. In a presentation by a scientist at this conference I was reminded just how major this contribution by horses and other equids and other perissodactyla can be, including especially rhinos but also in some habitats tapirs. This is a major justification for saving and restoring the wild horses, asses, onagers, zebras, rhinos and tapirs in many places throughout the world! Please use this in your fight for their salvation and that of their ecosystems!


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