Geoscience Reference
In-Depth Information
impacts on land systems dating to prehistory. The extinction of megafauna in Aus-
tralia and the Western Hemisphere, some 40-30,000 and 10,000 years ago, respec-
tively, apparently involved human-induced landscape changes in concert with
climate change (e.g., Martin, 2005). Biota exchanges and concomitant landscape
changes amplifi ed during the 'age of exploration' and European colonisation of
world also qualifi es as global-scale land change (Crosby, 1986). In retrospect, each
new techno-managerial phase of humankind has escalated change in the land
struc-
ture
of the earth system, with major consequences for ecosystem goods and services
and the provisioning of food, fuel, and shelter for humankind (Turner and McCand-
less, 2004; MEA, 2005). The entire land structure of some regions has long been
transformed (e.g., McNeill, 1992; Foster and Aber, 2004; Butzer, 2005; Kirch,
2005), and today the land-cover impacts of deforestation-forestation, cultivation,
pasture, arid land degradation and water withdrawal have reached a global dimen-
sion in magnitude and spatial reach. Croplands and pasture consume about 40
percent of land surface of the earth (Foley et al., 2005), gained at the expense of
forest and arid-land covers (Williams, 2005). An estimated 10-20 percent of arid
lands, which cover about 41 percent of the terrestrial surface of the earth (Reynolds
and Smith, 2002), is degraded from human activity. Agriculture consumes about
85 percent of annual global water withdrawal - that withdrawal now approaching
about 10 percent of renewable resources (Foley et al., 2005) - and rangelands house
some 3.3 billion cattle, sheep, and goats (Raven, 2002, p. 954). Including other land
uses - for example, settlements, roads, reservoirs, recreation areas - the land covers
of the world have been increasingly fragmented, with impacts ranging from access
to pollinators to threats of biota extinctions of biota globally (MEA, 2005).
These land changes have reached such a magnitude that they now affect the
function
of the earth system through impacts on albedo (refl ectivity) and biogeo-
chemical cycles (but see Ruddiman, 2005). Land-based activities usurp up to 40-60
percent of NPP (Vitousek et al., 1997; Rojstaczer et al., 2001). Synthetic nitrogen
production, dominated by fertilizer for agriculture, has superseded nature's fl ow of
nitrogen (Matson et al., 1997) and land uses, largely deforestation and tilling,
comprise about 30 percent of the source of anthropogenic carbon in the atmo-
sphere (Watson et al., 2000; Foley et al., 2005). Tropical deforestation, especially
in Amazonia, portends to have major consequences on global hydrologic cycle
(Zhang et al., 2001).
Institutional Response
These facets of land change were quickly recognised among the international and
multidisciplinary sciences addressing climate change (Intergovernmental Panel on
Climate Change, IPCC) and earth system science (International Geosphere-
Biosphere Programme, IGBP) and led them to call for improved understanding of
land dynamics with outputs complementary with their research agendas. The IGBP
approached the then budding International Human Dimensions Programme, request-
ing a joint international project on Land-Use/Cover Change agenda (LUCC). Given
that the IGBP already had strong programmes on the biophysical side of the land
change, LUCC focused on land-change observation and monitoring (remote sensing),
land processes and land-change (spatial) modelling, with the intent that the human
subsystem of the land would connect to the environment subsystem through land
cover (Gutman et al., 2004; Lambin and Geist, 2005).
