CLM20-2 full issue-1 - Flipbook - Page 26
A guide to conservation land management and greenhouse gas emissions
Creating swamp/fen on ex-arable on mineral soil
Rewetting drained bog
Creating lowland wet grassland on ex-arable on mineral soil
Creating intertidal habitat on ex-arable on mineral soil
Establishing broadleaved woodland on ex-arable on mineral soil
Creating lowland wet grassland on drained grassland on organic soil
Creating swamp/fen on drained grassland on organic soil
Creating lowland wet grassland on ex-arable on organic soil
Creating swamp/fen on ex-arable on organic soil
Creating wet woodland on ex-arable on organic soil
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Change in GWP100 (t CO2e per ha per year)
Figure 2. Expected climate benefits of different types of habitat restoration and creation. Figures
show the expected difference in GWP100 before and after the start of habitat creation/restoration, with bars
indicating variation in these figures as explained in the notes below. All of the values are negative, indicating
that the types of habitat creation/restoration shown all have a beneficial effect on the climate. It should be
noted that although creating wet grassland on drained grassland or ex-arable on organic soil greatly benefits
the climate, the wet grassland created nevertheless still produces a small warming effect. For creation of
swamp/fen and lowland wet grassland on organic soil, and for rewetting of drained bog, recently restored
habitat releases significant quantities of methane. For these types of restoration, we calculated the difference
in GWP100 between drained habitat and recently restored habitat (right-hand end of the range bar), and
between drained habitat and pristine habitat (left-hand end of the range bar). The main blue-grey bar
shows the mean of these two values. In the case of creation of swamp/fen on ex-arable, we show whether
or not the value of the GHG flux for the arable includes emissions from farming operations/production and
use of inorganic fertiliser. It is assumed that the change in GHG resulting from rewetting will eventually lie
somewhere between these two extremes. All of the arable from which these habitats are restored/created is
assumed to have been managed intensively. For the creation of dry native broadleaved woodland, lowland
wet grassland and intertidal habitat on ex-arable on mineral soil, we show the range of values, based on
whether or not the GHG flux from the arable includes emissions from farming operations/production and use
of inorganic fertiliser. Data are the same as those used for Figure 1, apart from the following. For intertidal,
we have assumed a 75:25 ratio of saltmarsh to mudflat, and for the former used the figure for saltmarsh
created through managed realignment from Burden et al. (2019) and for mudflat created through managed
realignment from Adams et al. (2012). Rewetted bog and rewetted swamp/fen information is from Table 4.1 in
Evans et al. (2017). Restored lowland wet grassland on organic soil from figures for Baker’s Fen and Tadham
Moor in Evans et al. (2016). Low-input grassland on ex-arable from Gregg et al. (2021).
benefits for wildlife, while also changing the
habitat from one that warms the atmosphere to
one that cools it (or that at least results in a far
lower level of warming) (see Figure 2).
A complication regarding the wider impacts
of converting ex-arable and improved grassland
to semi-natural habitat, is that it is impossible
to know the extent to which the resulting loss
of agricultural land might displace agricultural
production into other areas, which results in
equal or higher levels of warming – particularly if
that production is displaced overseas, to countries
where substantial loss of natural landcover to
agriculture still occurs.
Freshwater wetlands on organic soil
Creating freshwater wetlands on organic soil
affords great climate benefits per unit area,
primarily by reducing or preventing the very large
annual emissions of CO2 from the drained, and
particularly cultivated, organic soil. It is worth
pointing out, though, that most arable on former
peatlands in Britain now contains very little
former peat owing to past cultivation, meaning
that, in the long term, the quantity of CO2
prevented from being released through restoration
will be less than for upland peatlands that contain
greater depths of peat. Wetland creation will also
result in cessation of fertiliser application and
24 Conservation Land Management Summer 2022 | Vol. 20 No. 2
