Domestic
livestock is not the major cause of loss of wild mammals.
We
have all seen it, the graph showing that just 4% of the world’s mammals, by weight, are
wild; humans
account for 36%, and livestock for the remaining 60%.* It is certainly
deplorable that there are so few wild mammals. Most people using these figures
and probably most people hearing them, draw the conclusion that domestic
livestock has squeezed out wild animals. But that is a far too simplistic conclusion.
This is demonstrated both by large-scale top-down analysis and smaller scale
empirical evidence.
To begin with crop lands occupy 1.5 billion hectares
and around 1.6 billion hectares of grasslands are
effectively grazed by domestic livestock. This makes up 3.1 billion hectares out of a total of
14 billion hectares. Excluding barren lands (glaciers, rough mountains)
agriculture occupy “just” one third of total land area (which is of course
already a lot and perhaps too much).** Land-use can affect a bigger area then
it physically occupies, but clearly agriculture, whether cropping or grazing,
can’t be the main reason for why there is so little wild life in the 7 billion
hectares of “habitable” land which are not under agriculture management.
On a temporal scale, the decline of wild mammals often
predates agriculture expansion. This is apparent in the late Pleistocene megafauna
extinction taking place more than 10,000 years ago, well before agriculture and
domestication of livestock. There are still heated arguments over if hunting by
humans or climate change was the main cause, most likely they were combined. Some researchers have estimated that the total biomass of herbivores,
approximately a billion large bodied mammals, at that time equaled current biomass
of domestic animals. Regardless of the exact numbers it is apparent that the
total weight of wild mammals shrank considerably by this “event”, and that
mammal wild life hasn’t recovered since.
Finally, by using data for the total global primary
productivity (the net
photosynthesis so to say) one can see that of the total net primary production,
humans and their livestock “appropriate” around 20 percent for agriculture
purposes. This is of course bad enough, but it still means that there is
biological space left for many more mammals and other wild life.
*
Even if cattle, wheat and corn now grow where bison
previously roamed in North America, I have seen no convincing evidence that
that the extermination of bison was driven by agriculture expansion, but rather
by a combination of hunting, disease and indirect
effects caused by the decline in Native American populations and abilities to
manage the bison herds. Obviously, the
enormous expansion of both croplands and ranching in North America would have
collided with a bison herd of 60 million head, sooner or later. But cattle and
bison can co-exist: according to a study from Utah there is more competition between cattle and
jackrabbits than between cattle and bison when they share the same
resources.
The massive death of >500 million ungulates in Africa in the late 19th century i which both
domestic and (mostly) wild animals were victims was caused by Rinderpest, a
disease brought in by cattle from India. This could in some way be seen as
caused by “agriculture” in a wider sense, even if it was more a function of
humans moving animals around than agriculture as such as domestic cattle
already were all over Africa.
Research in Kenya show a certain level of competition
between cattle and small herbivores but not with bigger herbivores. The researchers suggest: “that interactions between livestock and wildlife
are contingent on rainfall and herbivore assemblage and represent a more richly
nuanced set of interactions than the longstanding assertion that cattle simply
compete with (grazing) wildlife”. Studying the populations of domestic cattle
and wild life in Northern Tanzania for 17 years, researchers concluded that while there was a high density of cattle and sheep
and goat “several wildlife species occurred at densities similar (zebra,
wildebeest, waterbuck, Kirk's dik-dik) or possibly even greater (giraffe,
eland, lesser kudu, Grant's gazelle, Thomson's gazelle) than in adjacent
national parks in the same ecosystem.” Research from South Africa shows that there is some competition between oribi
antelope and cattle. Cattle facilitate oribi grazing during the wet season
because cattle foraging produced high-quality grass regrowth. Despite this, they
found that “cattle foraging at high densities during the previous wet season
reduced the dry season availability of oribi's preferred grass species.”
In Sweden the number of wild animals have increased tremendously the
last 200 years. In the mid-19th century there were
just a few hundred roe deer, moose and red deer and now there are around
300,000, 240,000 and 26,000 respectively. Wild boars were exterminated in the
17th century and now there are some 350,000. Beavers were gone by 1870 and now
we have 100,000. Hunting of cranes and swans have just started again as their
numbers are causing problems for farmers. Even the predators are making
comeback. Meanwhile, the number of people, pigs and poultry has increased many
times. The acreage of arable land peaked in 1916 and the number of cattle
increased with 50% from 1866 to its peak 1936, after which it fell back to
levels lower than in the 19th century. This remarkable comeback of wild life is a result of many factors but
hunting regulation is the most important one.
Researchers studying the dynamics of domestic and wild herbivores in Norway conclude that total herbivore biomass decreased from 1949 to a minimum
in 1969 due to decreases in livestock biomass. Increasing wild herbivore
populations lead to an increase in total herbivore biomass by 2009. “Declines
in livestock biomass were a modest predictor of wildlife increases, suggesting
that competition with livestock has not been a major limiting factor of wild
herbivore populations over the past decades.” There has been a “notable
rewilding” in Norway. They conclude that “Norwegian herbivores remain mostly
regulated by management”, most notably hunting.
For fisheries and whaling the role of hunting and
overexploitation is even more obvious than for the land living animals.
For sure, there are many cases where the expansion of
farming causes habitat destruction and loss of wild life. The 2022 global Living Planet Index shows an average 69% decrease in
monitored wildlife populations between 1970 and 2018. A team of researchers studied the causes
for threats to 23,271 species, representing all terrestrial amphibians, birds
and mammals. The six major threats were agriculture, hunting and trapping,
logging, pollution, invasive species, and climate change. Their results show “that
agriculture and logging are pervasive in the tropics and that hunting and
trapping is the most geographically widespread threat to mammals and birds.
Additionally, current representations of human pressure underestimate the
overall pressure on biodiversity, due to the exclusion of threats such as
hunting and climate change.” Exactly how agriculture
threatens wild life is not made clear in the study.
The impact of farming depends a lot on the context,
which environment, which species of wildlife and of livestock respectively as
well as management. How we farm,
trade and eat is of critical importance: “In short, the impact of food
production on biodiversity arises not from a single fault, but from the nature
of the system as a whole”, according to a recent report by UNEP, Chatham House and Compassion in
World Farming.
When land is cleared and plowed and converted into
cropland most of the original flora and fauna will vanish from the place and a
few new ones will enter. By and large, crop farming and wild life are no good
mates, so there is quite a direct link between cropland expansion and reduction
in wild life. There are many things farmers can do to make cropping more
biodiversity friendly, but grazing animals, boars and other mammals will not be
welcome in croplands as little as grasshoppers or lice are.
For grasslands the story is quite different. If a
tropical rain forest is razed to provide grazing for cattle, biodiversity and
wild life till be harmed to a very large extent. But most grazing in the world
takes place in lands that have either been natural grasslands or which were
converted (or restored) to semi-natural grasslands since many centuries or
millennia (which is the case of many of Europe’s grasslands). Grazing animals can co-exist with many other mammals and the share of primary productivity that humans and their livestock take from
grasslands is much smaller than from croplands, where we take almost all. The biggest conflict is with predators even
if there are many examples of how domestic livestock can co-exist with
predators.
Some make the case that domestic livestock, in particular cattle, to
some extent can act as ecological replacement for now-extinct megaherbivores
and that they can maintain landscapes and functions that otherwise would be
lost (see for example here, here and here).
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One of our cows in our silvo-pastoral lands. Photo: Gunnar Rundgren.
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There are, obviously, many things farmers can do to protect
and promote wildlife. But that would be the subject of another set of articles.
You can find some examples here
and here.
For sure, the cow and the deer can easily co-exist. On our farm, there is plenty of wild-life co-existing with our small herd of five mother cows. There are deer, elk, boars, fox, voles, fox, the occassional lynx a huge number of birds including flocks of gees, cranes. In the grassland they all thrive and do little harm, in my field of vegetables, I chase them away.
*Interestingly, the weight of
arthropods is ten times more than the weight of livestock and the weight of all
the organisms in a living soil is much higher than any animals grazing on the
land.
** Many quote considerably higher
numbers, e.g. Our world in data. They classify almost all global grasslands as
grazing area for domestic livestock, but that is simply not correct. It is only
a minor part of the grasslands that are actually grazed. For a detailed
analysis see the supplement of Climate warming from managed grasslands cancels the
cooling effect of carbon sinks in sparsely grazed and natural grasslands by Jinfeng Chang et al (2021).