Climate Change, Grazing & Land Use March 2020
There is a lot of talk in conservation circles and the media on
the impact of land use on climate change. However it is a
complex subject and it would appear that carbon flows are not
understood by most; for example the difference between
carbon emissions from the use of fossil carbon and carbon
emissions which are merely recycling of atmospheric carbon.
When we burn fossil fuels we are adding new carbon to the
atmosphere, the cause of global warming. However when
animals belch methane this does not result in an increase on
atmospheric carbon: they are merely recycling the carbon
fixed by the plants they eat. Certainly the methane they belch
is a strong greenhouse gas, but its time in the atmosphere is
short compared to carbon dioxide.
Animal husbandry, particularly intensive farming, certainly
does release a new greenhouses to the atmosphere but this is
through the use of fossil carbon in transport, farm machinery,
fertiliser & pesticide production, and the processing of animal
feed. However most of these outputs will also apply to crop
growing as currently managed. The only way to reduce these
carbon outputs is replacement of fossil fuels with renewable
energy, with no input of fertilisers etc. dependent on fossil
fuels for their manufacture.
Otherwise moving to a vegetarian diet will not make much
difference to the climate! Certainly replacement of tropical
rainforest to animal pasture in some parts of the world does
add to the amount of carbon in the atmosphere, but this is
not relevant to UK farming.
In the UK before the advent of the industrial manufacture of
fertilisers, animals were an essential part of crop rotation,
the dunging effect of animals being essential to maintain
long-term soil fertility. If animals are no longer part of the
farming scene, then soil fertility can only be maintained
through the continual use of industrial-manufactured
fertilisers (although the use of legumes such as clover can
fulfil the nitrogen deficit). Can these be produced in a
carbon-neutral way? The return to more environmentally
extensive farming does rely on animals.
Additionally, a significant proportion of the UK’s biodiversity
is grazing dependent, such as chalk grassland, limestone
grassland and lowland heath: if animals are no longer part
of the agricultural scene, then this biodiversity will be lost.
And does wool not have a bright future as a non-fossil fuel,
Climate change mitigation & nature conservation not always on the same side!
There appears also to be a strong belief amongst conservationists that conservation of habitats
and climate mitigation are always on the same side, but there is no a priori reason why this
should be the case! There are times when, if we want to conserve the landscapes and natural
habitats of the UK, we will have to decide which is more important: climate mitigation or
preventing the loss of habitats.
The papers in this new ‘Climate change & land use’ section of my website address these issues,
and also point out that tree planting in the UK does not necessarily mitigate climate change.
The return of forestry ploughing for tree
establishment: an example of a land use
practice inimical to climate change
Many upland soils (podsols, peaty gleys, shallow
peats, deep peats) are tend to be inimical to good
tree growth. Hence the land is ploughed to break
open the impermeable ironpan, to access the
mineral soil below and to dry out the ground.
However these soils are carbon rich and left alone
will continue to accumulate carbon, perhaps more
than the trees will eventually fix. Ploughing will
release this stored carbon to the air, contributing to
Incidentally, the ploughing also destroys any existing
vegetation pattern, destroys any existing
archaeology in its path, increases the rate of water
run-off (contributing to downstream flooding) – and
adds permanent scars to the landscape (a network
of parallel lines).