- Livestock are the key to a healthy soil food web
- A healthy soil food web is necessary for sustainable food production
- Large numbers of livestock are necessary to maintain the soil food web
- Therefore large numbers of livestock are necessary for sustainable food production
*Note I am not going to be talking about the role of livestock in Brittle Environments in this article. Please refer to this article on the subject of livestock in Brittle Environments.
1. Livestock Are The Key To A Healthy Soil Food Web
Why are animals so important? Animals improve the health of the soil food web in three ways: they graze, they trample, and they digest. Lets look at each of these three functions to see why exactly they are necessary for soil food web health, and why livestock are our only option for providing these functions over most agricultural land on earth.
The Benefits Of Grazing
When a plant loses some or all of its above-ground leaves or stems (like when it is grazed) it will immediately try to regrow the lost material as fast as possible. It needs nutrients to regrow so it starts putting out huge amounts of energy (exudates) into the soil, far more than usual, in order to acquire these nutrients. This effectively puts the soil food web in overdrive for a little while. (for more information about this process see this post).
Because grassland plants have evolved alongside grazing animals they are able to recover from grazing very quickly. This allows the soil food web to be put into “overdrive” several times each year. This process increases the health and efficiency of the soil food web over time. It also physically increases the depth and organic matter content of the soil. (Note: plants must be allowed to recover after being grazed or the soil food web will eventually start to degrade. See “What Are Properly Managed Livestock” )
This is why grasslands have the deepest and richest soils on the planet: for millions of years animals have been eating the grass plants, each time they do the soil food web goes crazy. And when the soil food web goes crazy soil is created, fast.
After the animal’s graze the plant material goes through their digestive system and passes out later as feces. This process is also incredibly important, you will learn more about that later in the section called “The Power Of Digestion”.
Why Do We Need Livestock, Not Just Wild Animals, For Grazing?
The larger the proportion of the plant that is grazed, the greater the amount of energy (exudates) released by the plant into the soil because the plant is trying to regrow a greater amount of biomass. Therefore animals which eat more of each grass plant will have a greater positive effect on the soil food web.
If the recovery period before the plant is grazed again is too short the plant will be stunted. Stunted plants cannot contribute much, if at all, to the soil food web. So to get maximum benefit from grazing the recovery period must be long enough to allow the plant to prepare to be grazed again. An animal which returns to graze a plant too soon is not benefiting the soil food web.
Therefore we need animals which eat most of a plant, and then leave the plant alone for several months.
Deer tend to take small bites from many different plants, and they tend to return to a plant when the regrowth is still tender and delicious (way too short of a recovery period). Deer, and their relatives, cannot improve the soil food web with their grazing.
Smaller animals like mice, rabbits, and gophers exhibit the same behavior. They take small bites, and they return when the regrowth is most appetizing, which is far too soon for proper recovery.
There is only one category of wild animal which will do this reliably: large herbivores in a natural herd. The vast majority of agricultural areas do not have access to these natural herds anymore (Africa probably is the last place on Earth that this process happens naturally).
Livestock, on the other hand, can be controlled to eat a large portion of the plant and then allow it to recover fully. We cannot rely on wild animals to graze the land properly, we need livestock.
Why Can’t We Use Technology To Graze?
There are many machines which can perform the function of grazing (lawn mowers, industrial mowers, swathers, etc).
Most of them cut the vegetation which is slightly different than grazing because most animals pull the vegetation until it tears (allowing the plant to have some control over the grazing through its leaf and stem structure). There is no solid evidence about how important or unimportant the pulling-action of animal mouths are to plant health. Some farmers claim that the pulling action stimulates more biological activity around the roots of the plants. But lets assume that machines can perform the same grazing function as animals can…
Do you think machines should be used instead of animals? Ask yourself the following questions:
How many machines would it take to “graze” all agricultural land in the world at least once every couple of years (which is a very rough estimate of the ideal minimum amount of grazing needed)?
How much fuel would they use? What happens when fossil fuels become scarcer? (it is possible, of course, that at some point these machines could run off of renewable energy sources. But what should we do in the meantime?)
How would steep mountain slopes, woodlands, and wetlands (where machinery cannot go) receive the benefits of grazing except through animals?
Why would any farmer use a machine to graze (which costs money) instead of animals (which make money, and provide additional benefits)?
- Why would we use machines, which can only perform some of the functions needed, instead of animals which have a whole host of positive interactions with the soil, wildlife, and with the humans who manage them?
In conclusion, machines can be used to mimic livestock grazing action and improve the soil food web. But it is impractical, costly, and unsustainable to use machines on a large scale. Machines will no doubt continue to be important for certain landscapes (lawns, for example) but over the vast majority of land on Earth machinery cannot replace the grazing function of livestock.
* Note: If you are going to use machines to graze (or livestock for that matter) you must understand the importance of timing. The reason you do not see lawnmowers dramatically increasing the health of people’s lawns has to do with timing. Lawns are mowed too often. Grass plants must be allowed to fully recover before they are grazed/cut again otherwise their growth will slow over time, reducing and eventually eliminating the beneficial effects on the soil. Generally a grass plant has “fully recovered” when it starts to put out a seed head. “Grazing machinery” will not benefit the soil food web unless it is timed properly!
The Necessity Of Trampling
When an animal tramples a plant to the ground without eating it the stems are usually broken in the process, so from the plants point of view it is as if it had been grazed. So the soil food web kicks into high gear exactly like it does when plants are grazed. But trampling actually does even more than that…. trampling also deposits a layer of dead plant material onto the surface of the soil called “litter” or “mulch”.
Mulch, or litter, has the following benefits:
Reduces water evaporation from the soil
Provides habitat for bugs, rodents and other small organisms which are essential parts of any food chain. Without these organisms the soil food web itself would be negatively effected.
Creates organic matter. All of the plant material is eaten by soil microorganisms and incorporated into the soil where it can do its job of providing water and nutrients for years to come.
Protects the surface of the soil from extreme temperature fluctuations which are harmful to plants and soil organisms
Protects the soil surface from solar radiation which is deadly to most soil organisms
Without a litter layer on the soil surface the soil’s health will decline rapidly. Water will not be absorbed into the soil in sufficient quantities, and the soil itself will be lost via erosion. Eventually the soil will not be capable of growing anything but weeds. Maintaining a litter layer on the surface of the soil is a necessity for basic sustainable food production.
Note: Animals must be in a fairly high density “herd” in order to trample any significant amount of vegetation. See “Properly Managed Livestock”.
Why Do We Need Livestock, Not Just Wild Animals, For Trampling?
The heavier and larger the animal, the more types of vegetation it will trample onto the soil surface. (For example, an elephant (or a mammoth) can trample shrubs and small trees whereas a deer can only trample delicate grasses). The more vegetation trampled the greater the benefits to the soil food web.
The heavier the animal the tighter it packs the vegetation onto the surface of the soil. The more tightly packed the litter layer the faster it can decompose (especially in dry environments) and therefore the faster its nutrients are incorporated into the soil food web.
Normal animal behavior is to follow well-worn pathways. Animals must be either running away in fear, running towards something eagerly, or in a tightly packed herd in order to trample vegetation. Most animals spend a relatively small amount of their time running away in fear. If they can, they will run along pathways and therefore trample no vegetation. They spend even less time running towards something in anticipation. So the most practical way to get an animal to trample vegetation is to put it in a tightly bunched herd.
Therefore in order to receive the maximum soil food web benefits from trampling we need the tallest and heaviest animal possible and it must spend the most amount of time possible in a herd.
Deer cannot be kept in a tight bunch for very long, they are not herd animals and will not be happy with those conditions. Deer are also relatively light, and have small feet, meaning they do not do a very good job of trampling anything.
Smaller animals like rabbits, birds, and rodents are simply not heavy enough or tall enough to trample vegetation onto the soil surface.
Once again, in most areas of the world, we must use livestock in order to receive the soil food web benefits that result from animal trampling.
Why Can’t We Use Technology To Trample Instead Of Livestock?
There are also many machines which can trample vegetation. Some machines can even mimic animal hooves.
However trampling machinery faces the same problems as grazing machinery: it is simply too expensive and too energy intensive to use on a large enough scale to provide the essential service of trampling to all of the worlds agricultural land. Trampling machinery cannot access many areas of the world which are too steep, too heavily vegetated, or too wet.
So, yes machines can be used to replicate the trampling action of livestock. But they are not practical, except on a relatively small scale and in locations where livestock may not be allowed. Machines also cannot perform the other roles which animals provide for ecosystems like providing food for birds, food for dung beetles, etc. Machines are also not edible.
The Power Of Digestion
The environmental conditions inside an animal’s gut are far different than the conditions in the soil. The inside of an animal’s digestive system is anaerobic, always moist, and very warm. This means that different organisms and different chemical processes take place within animals, which can not be replicated anywhere else in nature.
This unique process recycles nutrients far faster than soil organisms ever can because the conditions in an animal’s gut are more conducive to chemical reactions. Plants have evolved in environments where animal feces were almost always available, so they have evolved to require these easily available nutrients for optimal growth.
In the absence of animals the store of easily available nutrients will eventually be depleted and plants will only be able to access nutrients as fast as small organisms can make them available (which is not very fast). Plants will begin to suffer and many will not be able to grow at all.
The only other source of these extra nutrients besides animals are fertilizers. The difference between animal manure and fertilizers is that animal manure (when deposited naturally) is not harmful to soil organisms, and animal manure is infinitely sustainable.
*Note: Animal poo is also an important source of microorganisms for soils which have lost their native microorganism populations.
Why Do We Need Livestock, Not Just Wild Animals, To Cycle Nutrients?
Most vegetation consists of mostly cellulose. An animal which can digest cellulose in its body will speed up the nutrient cycle more than an animal which leaves the cellulose in its feces where it must be slowly decomposed by soil organisms. Think about how long it takes a leaf to decompose on the surface of the soil, or even in the soil. Compare that with a ruminant which can decompose that leaf completely in a matter of hours!
All major terrestrial ecosystems evolved with cellulose-digesting animals, therefore plants have adapted to grow in ecosystems with very fast recycling of cellulose. Without cellulose-digesting animals plants will not grow to their full potential. Eventually this altered nutrient cycle may no longer be able to keep up with the needs of the plants in the area. It may take a long time for this deficiency to show up if plenty of non-ruminant animal digestion is taking place.
The higher the percentage of biomass digested by animals versus by soil organisms the faster the nutrient cycle and the more nutrients will be easily available for plant growth at all times. So the more an animal eats, the better (as long as plants are allowed to recover and there is a layer of “litter” on the surface of the soil).
Therefore an animal, or a population of animals, which can eat the most total vegetation and which can digest cellulose will provide the most benefits for the nutrient cycle.
Based on this information it seems likely that we need the largest herbivores that we can find. In many areas cattle are the largest animal available. There may be larger animals available (like moose, horses, bison, etc) but if their population is small than they will not be able to compete with a large herd of cattle in terms of their effect on nutrient cycles. Likewise a large herd of sheep will have a greater effect on a given area than a small number of cattle.
Of course there is a limit to the number of animals any ecosystem can support, and going over that limit would start to degrade the ecosystem. So to have the maximum benefit to the nutrient cycling of an ecosystem we need to have the maximum population of grazing animals that can live on the land without overgrazing it.
Why Can’t We Use Technology To Replace Livestock Nutrient Cycling?
There are two ways in which technology might help us replace the nutrient cycling functions of livestock: composting/fermentation, and redistributing human wastes.
It is definitely conceivable that fermentation process could mimic the conditions inside the digestive system of livestock. The temperature would need to be maintained within a very narrow range, oxygen would have to be excluded from the process, the base material would need to be shredded (chewing) and then bathed in acids and enzimes (stomach), moisture would need to be constant and evenly distributed, and the specific organisms which live in digestive systems would need to be applied to the compost. Composting on a large enough scale to replace animal manure would b very costly and energy intensive.
Expensive machinery would be required to harvest the compost base material and then again to distribute the compost over the land, whereas animals distribute their manure for free. Once again this sort of technology-intensive solution is just not a practical or sustainable way of distributing nutrients over the vast landscapes of the Earth. Although it is certainly a useful technology that we should be using in situations where livestock are not practical.
Human waste should definitely be put back onto the land, where it is a benefit to the environment, instead of being put into our waterways where it causes tremendous harm. However, there are a lot of logistical problems in accomplishing this.
Most people live in cities. In order to use humanure to fertilize our agricultural land it would need to be transported out of cities and then spread evenly on the land. Considering the volumes of humanure that would be produced by the average city every day you can see how distributing this manure would be tremendously expensive. There would also be pathogen problems, the humanure would probably need to be fermented or processed before being put on the land to remove human pathogens. I am not saying we shouldn’t try to make it happen, but I am saying it is very unlikely to happen anytime soon and when it does happen it is unlikely to be a practical, or economical way of fertilizing most of the world’s farmland.
There is a second problem with humanure; humans cannot digest cellulose. Cellulose is the most abundant plant material on earth, but it is very hard to break down. Only large herbivores (mostly ruminants) can break down cellulose rapidly. If a cow eats a leaf from a tree (which they do, if given the chance) that leaf will be completely decomposed in 1-3 days. Think about how long it would take that same leaf to decompose if it were just sitting on the forest floor? (months or even years) Clearly animals that can digest cellulose significantly increase the speed of nutrient recycling. In human feces cellulose passes through undigested, it must then be digested further by the slow-working soil organisms before it can be used by plants. Humans, in otherwords, are not as effective at recycling most organic matter as livestock are. Large cellulose-digesting herbivores used to roam every continent on Earth in huge numbers. It is only logical that plants would have evolved to require the very rapid nutrient cycle provided by these animals. Humans cannot replicate this without using livestock.
Recent research has indicated that large animals are also essential for spreading nutrients around the globe and counteracting the natural effect of gravity (which is to move everything downhill, into valleys and eventually into the ocean). (Reference) An animal eats a marsh plant, walks up a hill, and then defecates, depositing the marsh nutrients onto the hill. Without animals highlands and hills will eventually lack the nutrients needed to sustain their ecosystems.
All of this applies to farmland as well as natural ecosystems.
Why Do We Need Livestock, Not Just Wild Animals, For Nutrient Distribution?
The research specifically implicates large herbivores as being essential for this process. But why?
Larger animals more nutrients in their guts while they travel.
Larger animals can usually travel longer distances than smaller animals.
The larger stride of big animals also makes it easier for them to travel uphill.
So which animals are needed to perform this function on agricultural land?
Most agricultural land has fences or infrastructure which prevents wild animals from roaming freely and depositing nutrients far and wide.
Most deer, and similar large wild animals, hang out it woodlands. In many areas woodlands occur in the valleys while the hills are grassy. This means that most of the time the deer will not be transporting nutrients from the low to the high areas.
- There are no animals left in most areas of the world which can transport as many nutrients (by volume) as a cow can. Cows have big bellies!
Once again it makes the most sense to use livestock to fill this role. Livestock can transport large quantities of nutrients long distances. Livestock can also be consciously used to deposit nutrients on slopes and high ground if the grazing is planned carefully (there are many people already doing this).
A Summary Of Why Livestock Are Necessary For A Healthy Soil Food Web
Livestock are necessary because:
- Grazing of vegetation stimulates the soil food web. The more grazing (as long as it is properly managed) the healthier the soil food web becomes over time. Grazing increases the depth of the soil and increases soil organic matter content. Beneficial grazing cannot be accomplished over most of the world’s land with technology or by wild animals, livestock are our only option.
Trampling of vegetation to create a “litter layer” can only be accomplished with livestock, not wild animals or technology, on most of the Earth’s surface. Constantly maintaining a litter layer on the surface of the soil is the key to maintaining the soil health necessary for sustainable food production.
Most plants, including food plants, have evolved with access to the rapid nutrient cycle which can only be provided sustainably with animal poo. Without the periodic deposition of animal manure plants will become unhealthy and unproductive. Some will eventually stop growing altogether. Livestock preform this nutrient cycling function far more effectively than any wild animals or technology can over most of the Earth’s landscapes.
- In order to combat gravity and move nutrients uphill in our farm ecosystems we need livestock. They are large, can travel long distances, and we can precisely control how they move nutrients around the landscape. If we do not use livestock for this purpose lands at higher elevation will lose their soil and nutrients over time, making them inhospitable for agriculture and for natural ecosystems as well.
2. A Healthy Soil Food Web Is Necessary For Sustainable Food Production
I have written an in-depth article about the the necessity of healthy soil food web for sustainable food production. You can read that article here, but here is a quick summary:
- A healthy soil food web is responsible for the productivity of agriculture, and, therefore, the price of food and the total amount of land needed to produce our food. If the soil food web falls below a certain level of health agriculture will not be productive enough to sustain our population.
- A healthy soil food web is necessary to mitigate droughts and reduce irrigation needs. Below a certain threshold of soil food web health most areas in the world will not have enough fresh water to reliably produce food in the future.
- A healthy soil food web is the key to preventing diseases and pest problems in our crops. Pesticides are continuing to new pesticides, with every increasing levels of pesticides being required every year. Clearly this is not a sustainable model. There will eventually come a time when we will be forced to employ the natural pest protection services of a healthy soil food web or face the widespread loss of food crops.
- The soil food web is responsible for supplying plants with all of their nutrients. If the soil food web is not healthy than plants will be nutrient deficient, and these nutrient deficiencies will be passed on to the animals or humans that consume them. If the soil food web is not healthy enough than human nutrition will suffer (we are already seeing the effects of this).
3. LARGE NUMBERS OF LIVESTOCK ARE NECESSARY
So we need livestock. But how many do we need?
We do not know for sure how many livestock we need because there is a tremendous lack of research in this area (the vast majority of agricultural research funding generally goes to the latest chemical, tractor, or GMO, not into researching sustainable alternatives).
The missing information we need in order to determine the bare minimum number of livestock necessary:
- How frequently must vegetation be trampled in various climates in order to maintain a constant litter layer? (my personal guess is that trampling must be applied ever 2-3 years in most climates, but that is only based on personal observation, we need research!)
- How many livestock are needed to achieve this rate of trampling over all of the world’s farmland? (Based on personal observation of high density livestock I would estimate that 40 cattle can trample 1 acre/ day)
- How frequently must vegetation be grazed in order to maintain reasonable levels of soil health over a very long period of time? (I have no idea)
- How many livestock are needed to achieve this rate of grazing over all of the world’s farmland?
- How many livestock are needed to provide the soil and plants with the manure (nutrient cycling) that they need? (probably a similar number to the numbers of mega-fauna which used to roam the earth)
- How many livestock are needed to counteract the constant movement of nutrients downhill over an indefinite period of time? (no idea)
We can use my extremely rough estimations to get some idea of how many livestock would be needed at a bare minimum in the United States and Canada (which are the areas I have experience with).
- Every acre of farmland (not including existing pasture land, which is often too poor quality to produce other crops) in must be trampled every 2.5 years to maintain soil health.
- There are 90 million acres of cropland in Canada and 408 million acres in the United States. (roughly 500,000,000 acres total)
- So there would need to be enough livestock (we’ll assume they’re all cattle) to trample 200 millions acres of land once every year.
- Using my estimate that it takes 40 cattle to trample 1 acre in 1 day we can calculate that in order to maintain the minimum soil health of all existing cropland in the US and Canada I estimate that we need to put about 22 million cattle on that cropland permanently. (Plus the cattle needed to maintain the other ecosystems in Canada and the US)
This is estimate was based on extremely limited data, so it is probably very inaccurate. (haha). More research is needed!
We do, however, have some very good reasons to believe that a lot of livestock are necessary, possibly far more than are currently being raised! Here are the reasons we need large numbers of properly managed livestock:
- The more properly managed livestock on our cropland the greater the benefits to the soil food web. In other words, the more properly managed livestock on our cropland…. (reference)
- The less total land area needed for human food production
- The less total amount of water needed for irrigation
- The less pesticides needed for crop production
- The lower the price of food
- The more nutritious the food produced.
- Ecosystems, and individual organisms, tend to function most efficiently and productively in the same conditions they evolved in. Almost all ecosystems on earth evolved with large numbers of megafauna (huge animals), and most of these megafauna moved in herds to avoid mega-predators. (reference) These megafauna only went extinct relatively recently (10-50 thousand years ago depending on location) so most ecosystems have probably not had enough time to evolve adaptions to their absence (considering those megafauna have been around for at least 5 million years, 100 x longer than they have been extinct). We can therefore assume that most ecosystems on Earth need the ecosystem functions provided by these extinct megafauna in order to be at their most healthy and productive state. The only method available to replicate these extinct megafauna is properly managed livestock. Especially cattle, horses, and other large livestock. Mamoths would be way better!
In summary, we do not know the bare minimum number of livestock necessary to maintain our basic food production needs. I estimate that in Canada and the US we might need 22 million cattle just to maintain existing cropland soil health.
But why settle for the bare minimum soil health? We have many good reasons to strive for maximum soil health (see them above) which would mean putting as many properly managed livestock on our land as possible.
Livestock are necessary for maintaining healthy soil food webs on our agricultural land. Their trampling, grazing, and digestive systems cannot be replaced by wild animals or by technology. Additionally, maintaining healthy soil food webs is a basic prerequisite to sustainable food production. Without healthy soil food webs we agriculture simply cannot sustain our needs into the future. In order to provide all agricultural land with grazing, trampling and manure we need large numbers of livestock.
Therefore, for food production to be sustainable, large numbers of livestock are a necessity!
*Note: Everything in this article was written with Non-Brittle Environments in mind. Brittle Environments have an even greater need for livestock, for different reasons. Read about why Brittle Environments require livestock here.