This week I will be reviewing a more technical article
compared to that of the past two weeks. Thus far, all my blog posts have been
on climate change and I have not explicitly touched on the issues of land-use
change and its attendant effects on the environment. As such, I decided to look
for an article that would touch on both climate and land-use change, which I believe
to be interrelated and influence each other through feedback mechanisms.
Titled ‘Projected land-cover change effects on East Africanrainfall under climate change’ (Moore et
al. 2015), the study assesses the impacts of land-cover change and climate
change separately, and together on rainfall in parts of East Africa, to access
the relative magnitude of each, using four different scenarios:
- Current land-cover and current climate
- Current land-cover and future climate
- Future land-cover and current climate
- Future land-cover and future climate
The results of the study found that greenhouse gases (GHG)
in general, lead to wide-scale, and usually more severe impacts compared to the
effects of land cover/land-use change (LCLUC) which are more regional or local.
LCLUC can affect precipitation in a variety of ways. The change from forest to
cropland for instance, can result in an increase in albedo and in turn surface
cooling, which reduces convective rainfall. Overgrazing removes large stretches
of vegetation which increases the amount of suspended dust, resulting in
radiative cooling and therefore a decline in (convective) precipitation. Under
LCLUC, short heat-flux and long heat-flux may also be intensified, resulting in
strengthened sea breeze and land breeze effect (due to greater heat differential
between land and sea), which intensifies precipitation over and around the
lakes. This is because heat differential between the large lakes of East Africa
and the surrounding land result in diurnal variations in precipitation—rainfall
occurs over the shore during the day and evening (when the land is warm than
the lake) and over the lakes in the night and early morning (when the land is
cooler than the lake) (Ba and Nicholson 1998). The intensification of rainfall
along coastal areas where forests have been replaced with agriculture can
potentially exacerbate the risk of floods caused by GHG, resulting in agricultural
damage.
In terms of the relative impacts of LCLUC and GHG, the
influence of LCLUC was as large or larger than that of GHG—approximately 25% of
the domain. The precipitation in areas which had higher population density were
naturally more influenced by LCLUC as there were more human and agricultural systems.
Evidently, LCLUC in developing countries have a first-order impact on local
rainfall.
My thoughts after
reading the paper:
This paper has demonstrated, in the context of East Africa
that climate change and land-use change are related processes. Both have
effects on precipitation, though at different scales—the effects of land-use change
are more pronounced at a local level, while the effects of climate change are usually
broader. That said, the effects differ across the region due to other physical
factors, such as topography and population density.
In my previous posts, I have focused mainly on the effects
of climate change on water in Africa, and in turn the production of food, since
water is needed for irrigation. The article, however, presents the other side
of the coin—how the conversion of forest to farmland for irrigation may result
in the development of a positive feedback mechanism that prevents precipitation
and reinforces drought conditions (due to higher albedo, radiative cooling and
high pressure conditions at the surface).
Therefore, in addition to implementing strategies that focus
on the provision of safe water e.g. the building of covered wells and
handpumps, I believe it is worth considering how land-use can be managed sustainably to meet the population’s needs while
minimising the overall impact on precipitation and hydrological conditions. I
hope to be able to find case studies where the effects of land-use change on
climate have been taken into account in land-use management, which I may
reflect on my next post.
Thanks for reading and till next time~
