Conservation and Sustainable Use of the Biosphere - WBGU

Sustainable land use E 3.3
145
Table E 3.3-3
Agricultural land 1994, sub-divided according to arable and
permanent grassland.
Sources: WRI, 1998a; FAO, 1998b; World Bank, 1998
respect to agricultural land vary greatly in the different
regions, as shown in Table E 3.3-3.
If we look at the supply of individual regions or
countries, this does not always have to be secured
from their own agricultural land. As a result of a disproportionate
increase in production in favourable
areas, shortages in deficit regions can be balanced out
if trade and distribution systems enable this.
E 3.3.4.1
Extending agricultural acreage
Arable land Grassland
[ha per inhabitant]
North America 0.79 0.9
Latin America 0.36 1.5
Africa 0.27 1.3
Europe 0.43 0.24
Germany 0.15 0.07
Asia 0.18 0.3
China 0.08 0.33
Developing countries 0.18 0.49
Developed countries 0.57 1.0
Over the last few years various estimates of potential
arable land have been published. The estimates
worldwide amounts to 2–4 thousand million ha
(Alexandratos, 1995; Luyten, 1995; Fischer and
Heilig, 1998). Of these, around 1.5 thousand million
are already being cultivated today (FAO, 1998b).This
total agricultural land has remained more or less constant
over the last twenty years in spite of additional
cultivated land.As a result of soil erosion, salinization
and the spread of settlements, transport routes and
deserts, almost as much land has been lost as has
been claimed.
Fig. 3.3-4 shows some scenarios of how the need
for agricultural land will develop worldwide with a
growing population and varying production levels. A
required area of 0.28 ha per person was used as a
basis to calculate the scenarios shown in the diagram;
a value that already today cannot be reached in large
parts of Asia and on average throughout the globe
for developing countries (Table E 3.3-3).The calculation
also presupposes that in future no agricultural
land will be lost to soil degradation. This is an optimistic
assumption because soil degradation is currently
taking place on a large scale (WBGU, 1995a).
On the basis of existing productivity, the potential
land area would be sufficient to feed 12 thousand
million people. However, this calculation is deceptive
for several reasons. The current annual expansion of
agricultural land is only 0.1 per cent of the acreage
because at the same time similar quantities of land
have to be taken out of production due to severe
degradation (Alexandratos, 1995; Young, 1998).
Around 40 per cent of food production today comes
from irrigated farming, which accounts for around 17
per cent of acreage (FAO, 1996a).The area dedicated
to this type of farming has increased by a factor of 2.5
since 1950 (Young, 1998). However, the growth of
irrigated land will not continue at the same rate as in
the past because of limited land availability, high
development and maintenance costs, increasing
impairment from salinization and limited availability
of water resources. On the contrary, over the last two
decades the growth rates have fallen markedly. In
Asia, the most significant region of the world for irrigation
farming (62 per cent of acreage), 85 per cent of
water extraction is already used for agriculture, and
in the countries with the highest populations, China
and India, the available water potential has already
been exhausted by over 80 per cent (Kulshreshta,
1993; WGBU, 1998a).
The expansion of agricultural land is far from
being a certainty and is possible to varying degrees in
different regions. Whereas in south-east Asia or
north Africa around 85 per cent of the potential areas
are already being used, the proportion used in South
America is only 20 per cent (Young, 1998). Under the
outlook of conserving biodiversity, a strategy of
major expansion of agricultural land should be
viewed extremely critically; after all, it aims at continued
progressive intervention in natural ecosystems,
increasingly encroaching on more marginal
sites and thus also destroying sites of high biodiversity.
In particular, in addition to their high genetic,
species and habitat diversity, the fragile tropical and
subtropical ecosystems play a significant role as gene
pools (gene centres) for many domesticated plant
and animal species (Section D 3.4). The expansion of
agricultural use in these areas would therefore be
associated with considerable risk because previously
unused resources would be destroyed and the genetic
basis of cultivated plants would be threatened.
The following conclusions can be drawn from this
brief overview:
• All possible steps must be taken to put a stop to
the global degradation of soils so that the land
already under cultivation does not lose its productivity
(WBGU, 1995a).
• The expansion of the agricultural land at the
expense of natural ecosystems should take place
only to the extent that is unavoidable following
exhaustion of the production potential on land
areas already cultivated.