Page 14 - Module_5

This is a SEO version of Module_5. Click here to view full version

« Previous Page Table of Contents Next Page »
14
FAO/UNEP/UN-Energy Bioenergy Decision Support Tool -
MODULE 5: Land Resources
if necessary, land management regimes. The output of this
step is a set of mapped landscape strata.
Identifcation of the suitable set of indicator variables
appropriate to the required scale, and for each of the degrad-
ing processes at work (i.e. physical, chemical and biological)
for recognized and mapped strata of land.
Identifcation of the measuring/modelling methods and tools
for the identifed indicators as appropriate to the ecology of
lands under consideration. The LADA project (Box 2) has
identifed a comprehensive set of indicators for the main
types of degradation (LADA, 2008). These indicators can be
adapted to the circumstances of the assessment.
• Determination of a suitable algorithm for combining the
values of indicators derived from feld assessment and
modelling results.
• The assessment could be used to assess the potential for
bioenergy, although additional assumptions and data would
be needed.
BIOENERGY POTENTIAL ON DEGRADED LAND
The potential of bioenergy on degraded or marginal lands
depends on a variety of factors that determine the yields that
can be achieved and the inputs required; estimated potentials
for various world regions are estimated using imaging data,
crop growth models and/or additional information on soils and
climatic conditions. The actual yield for a particular crop in a
specifc location would nevertheless be subject to a different
set of parameters altogether since site-specifc factors could
predominate over the aggregate conditions. Table 5 shows a
summary of some global estimates developed from geographi-
cally disaggregated data; they suggest a fairly signifcant potential.
Several estimates are in the range of 25-50 EJ, which amounts to
5-10% of current global energy consumption.
SOCIO-ECONOMICS OF MARGINAL/DEGRADED
LAND
Great care should be taken when judging land as marginal and/
or non-productive. Current land use patterns must be analysed
systematically, and in a given context land tenure structures and
rights need to be considered. Low-yield land is often used for
grazing and in many cases is fundamental for the subsistence of
the poor, as a source of fuel, food, medicinal plants and grazing
for animals. Many subsistence farmers use low-yield land for
growing their subsistence crops. There are millions of pastoralists
who depend on semi-arid low-yield land for feeding their herds,
whose production is often signifcant for the national economy.
In some cases, land is used by more than one user group.
Overlapping uses exist, for instance, where herding takes place
on crop land between growing seasons and when the land lies
fallow. Pastoralists can be quite effcient in their methods of
land use, although the pace of economic development tends to
increase their vulnerability, reduce their adaptive capacity and
contribute to unsustainable grazing patterns. Pastoralists (and
their production strategies) are often poorly documented and their
mobility complicates quantifcation and resource mapping. Any
attempt to map marginal land should be performed in dialogue
with local groups that know more about how the cultivation of
bioenergy crops may impact their livelihoods.
Seemingly marginal and unproductive land may also fll invaluable
roles in providing environmental services, such as wildlife corridors
and for the fltration and maintenance of water quality. Displace-
ment of such functions may disrupt important balances with
consequences outweighing any environmental benefts from the
bioenergy production.
Table 5: Estimates of global bioenergy potential on degraded or marginal lands
Source
Lands included
Area
(million ha)
Biomass yield
(t/ha/year)
Bioenergy Potential
(exajoules)
Van Vuuren et al, 2009
Global degraded lands not in use as
forest, cropland, pastoral land or urban. n/a
2.5 - 33
31
Hoogwijk et al, 2003
Abandoned agricultural land and
degraded grassland systems
430-580
1 - 10
8 - 110
Tilman et al, 2006
Agriculturally abandoned and degraded
lands
500
4.74
45
Field et al, 2008
Abandoned pastoral lands and croplands
not in use as urban or forest
386
3.55
27
Campbell, 2008
Abandoned pastoral lands and croplands
not in use as urban or forest
385-472
4.3
32-41