ECI Annual Review 2006/2007 - Environmental Change Institute ...

6
LAnd Degradation
The year 2007 saw the long-awaited publication of Soil Erosion in Europe (eds
Boardman and Poesen). This is the first state-of-the-art review of erosion in
34 European countries plus consideration of many practical and policy related
issues. The 58 chapter book resulted from a four year EU funded COST Action
involving 21 countries chaired by John Boardman.
John’s own work on erosion in Britain continues, especially in wet autumns
such as 2006. The focus recently has been on serious erosion in the Midhurst
area of West Sussex, where soil from eroding potato and maize fields reaches
the River Rother. This is a valuable trout stream and sediment impacts on
the gravel bed to inhibit breeding. Such ‘off-farm’ effects of erosion are now
accepted in Europe as of major societal concern. Complex relationships
between land owner, tenant farmer, highway authorities, fisheries interests,
local conservation schemes and the regulatory authority for rivers (the
Environment Agency) are being explored.
The idea of ‘desertification’ has been
widely applied to recent landscape
change in South Africa. Alarmist
fears of creeping desertification have
been expressed. Most researchers
have concentrated on vegetation,
identifying a change from mixed grass
and shrub to predominantly shrub
in the semi-arid Karoo. For farmers,
the implication is a loss of palatable
grazing.
The ECI is gaining new insights into
land degradation by studying changes
in specific landscape signatures -
badlands and deep gully systems. We
are collaborating with the University
of Cape Town and Rhodes University
in South Africa and the Universities of
Coventry and Leicester in the UK.
The Karoo
Erosion in the Karoo is typified by
heavily eroded ‘badland’ areas and
deep gully systems. For the past 10
years we have concentrated on an
area of the Klein Seekoei valley in
the Sneeuberg uplands about 70 km
north of the town of Graff Reinet. The
valley is wetter than the lowland Karoo
because of its altitude (ca. 1600 m)
and is an area of sheep farming. In
the past, the valley bottoms (‘lands’)
were used to grow wheat.
There is some evidence in the
Karoo as a whole, and in the Klein
Seekoei valley, that very high stock
numbers (sheep largely) are the
cause of vegetation change and soil
erosion leading to the formation of
badlands and gully systems. We are
investigating:
• the initiation of badlands and
gullies;
• the physical processes associated
with formation and development of
badlands and gullies;
• changes in the degraded areas
through time;
• the knowledge and attitudes of the
farming community;
• the possibilities for rehabilitation
of degraded areas;
• the impact of erosion on
hydrology, particularly dams and
water quality;
• rainfall patterns and climate
change;
• dam sedimentation and changing
patterns of pollen, Cs-137 and
Pb-210 ;
• the fire history of the area.
Methods
The topic requires an interdisciplinary
approach using methodologies from
natural and social science, including:
• monitoring of selected sites for
change;
• mapping of degraded areas using
air photographs from 1945, 1980
and 2000;
• simulated rainfall experiments;
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Leader:
Dr John Boardman
Land Degradation in the Karoo, South Africa
assembly of database on small
dams;
dating of sediment infill in small
dams (NERC funded project);
interviewing of farmers;
coring of willows.
Findings
The interaction of management,
especially severe overgrazing in
the past, and wet/dry periods (with
limited evidence of climate change)
seems to explain present degraded
landscapes.
Key Publications
Boardman, J., 2006. Soil erosion
science: reflections on the
limitations of current approaches.
Catena 68: 78-86.
Boardman, J. and Poesen,
J., 2006. Soil erosion across
Europe: major processes
causes and consequences. In:
J. Boardman and J. Poesen.
(Editors), Soil Erosion in Europe.
Wiley, Chichester. 479-487 pp.
Keay-Bright, J. and Boardman,
J., 2006. Changes in the distribution
of degraded land over
time in central Karoo, South
Africa. Catena, 67: 1-14.