CLM20-2 full issue-1 - Flipbook - Page 28
A guide to conservation land management and greenhouse gas emissions
Intertidal habitat
Creating intertidal habitat on ex-arable and
agriculturally improved grassland through
managed realignment benefits both wildlife and
the climate, and can provide overall economic
benefits to society (e.g. Natural Capital
Committee 2013; MacDonald et al. 2017).
These climate benefits arise through replacing
the warming effects of arable and agriculturally
improved grassland, with the moderate cooling
effect produced by the intertidal habitat. In most
cases, the economic value of these climate benefits
will be far lower than the flood-risk management
benefits of such schemes. For example, estimates
of the climate benefits of a 184ha intertidal
habitat-creation scheme at Medmerry in West
Sussex were £3.3 million over 100 years,
compared to flood-risk management benefits of
£78 million over the same period (Environment
Agency 2017), although the economic benefits
of climate regulation will inevitably increase
significantly in future due to increases in the price
of carbon. Despite the overall economic benefits of
intertidal habitat creation, this is not a particularly
cost-effective way to cool the climate, because of
the usually very high cost per unit area of most
managed realignment schemes (ABPmer 2015).
Native woodland
Establishing native woodland on ex-arable or
grassland on mineral soil will increase the rate
that CO2 is removed from the atmosphere, and
also the rate at which carbon is subsequently
stored in the vegetation and soil. Establishing ‘dry’
woodland on peat or organic soil is not desirable,
as this would increase its rate of drying and
thereby increase the release of CO2 from the soil.
We would also obviously not want to establish
woodland in areas of open habitat of high
conservation value, or in locations where it would
otherwise impinge on nearby open habitats.
Increasing the cooling effect caused by
ongoing conservation land management
Reducing the quantity of vegetation
removed
Reducing the quantity of vegetation removed
from a site will allow more carbon to accumulate
in the vegetation, soil, peat or buried sediment.
Examples of this might include ceasing or
reducing the intensity of management of
grassland and swamp/fen to allow these
habitats to develop into woodland and scrub.
Such changes would obviously conflict with
conservation objectives aimed at maintaining
wildlife-rich early successional habitat. There
may, though, be situations where it is possible
to reduce the intensity of vegetation removal
through cutting or grazing while also improving
an area’s conservation interest, for instance by
allowing the development of scrub and woodland
on grassland that is otherwise poor for wildlife.
Felling trees as part of conservation
management can cause consternation among the
general public, both due to people’s love of trees
but nowadays also because of the high profile that
trees have received for their role in helping address
the climate crisis. As always, it is valuable to put
the impacts of such activities into perspective.
During the first hundred years following
establishment, 1ha of lowland broadleaved
woodland typically removes an average of
around seven tonnes of CO2 per year (see Figure
1), which is equivalent to about 70% of the
average annual GHG emissions produced by the
activities of one UK citizen (see earlier). Based on
this, felling a 30m × 30m area of woodland, for
example, would reduce the annual rate of cooling
of the atmosphere by the equivalent of about 6%
of the average annual level of warming caused by
the activity of one UK citizen.
Changing the method of vegetation
removal
This involves changing the method of vegetation
removal to one that results in less warming for
the same quantity of vegetation removed. Two
approaches are often suggested. First, replacing
livestock with animals that release lower levels
of methane per quantity of vegetation removed.
Second, replacing livestock with cutting and
removal of vegetation.
Differences in the quantity of methane released
by different types of livestock are shown in Table
1. Cattle and sheep are ruminants and emit
far larger quantities of methane per quantity
of vegetation removed than ponies, which are
non-ruminants. Cattle are often highlighted as
releasing particularly large quantities of methane
26 Conservation Land Management Summer 2022 | Vol. 20 No. 2
