UN Population Division, Department of Economic and Social Affairs,
with support from the UN Population Fund (UNFPA)
|
| UN Population Division, Department of Economic and Social Affairs, with support from the UN Population Fund (UNFPA) |
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This document is being made available by the Population Information
Network (POPIN) of the United Nations Population Division (DESIPA), in
collaboration with the Population Programme Service, Women and Population
Division of the Food and Agriculture Organization of the United Nations.
For further information, please contact Mr. Jacques du Guerny, Chief of
the Population Programme Service, via email: jacques.duguerny@fao.org
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From: Population and Land Degredation. Rome: FAO, Women and Population
Division, Population Programme Service, September 1995.
ANNEX 1
FIGURE 4
THE EARTH LAND
TOTAL AREA: 13 BILLION HECTARES
*"Other land" includes barren and developed land.
================================================================
SOIL AS A CRITICAL NATURAL RESOURCE
Soil-is much more than a simple medium for crop production.
It is a dynamic ecosystem, a living membrane that cycles life-
sustaining nutrients between bedrock and atmosphere. Good soils are
home to some of the world's highest and most diverse Population of
species, including earthworms, insects and microorganisms that help
plants absorb nutrients and even protect against disease.23/ These
organisms break down dead plant and animal tissue to form humus, the
dark and crumbly carbon-based portion of soil. Healthy soils rich
in humus soak up water, invite airflow and resist erosion. Humus-
poor soils shed water, restrict root growth and break apart in rough
weather. Soil ecosystems are threatened by the progressive loss of
organic material as farmers abandon organic for chemical fertilizers
and offer the land less fallow, or resting, time. Currently,
however, little research is being conducted on the species
composition and biological properties of soils.
Soil may hold three times as much carbon as all the world's
plants, 24/ but its carbon content is diminishing. Since the drawn
of agriculture, an estimated 60 billion tons of soil carbon have
risen from the soil to the atmosphere as climate-warming carbon
dioxide. This amount is equivalent to a decade of global fossil fuel
combustion at current rates.25/
Cultivated soils lose not only humus and organisms but also
micronutrients needed for plant and human health. Fertilizers
replace nitrogen, phosphorus and potassium in soils, but rarely much
else. As crop after crop is reaped front the soil and shipped
elsewhere, with little return of comparable organic material to the
soil, there is no assurance that sufficient micronutrients will
remain in the soil for future crops and future generations.26/, 27/
23. Committee on International Soil and Water Research and
Development, 1991. Toward Sustainability: Soil and Water
Research Priorities for Developing Countries. Washington, DC:
National Academy Press.
24. National Research council, 1993. Sustainable Agriculture and
the Environment in the Humid Tropics. Washington, Dc:
National Academy Press.
25. Kevin G. Harrison, Wallace S. Broecker and Georges Bonani 1993.
"The Effect of Changing Land Use on Soil Radiocarbon".
Science, vol. 262 (October 29).
26. Margaret R. Biswas, 1994. "Agriculture and Environment: A
Review, 1972-1992." Ambio, vol. 23, No. 3 (May).
27. Judith McGuire, 1993. "Addressing Micronutrient Malnutrition."
SCN News. No. 9, United Nations Administrative Committee on
Coordination.
Source: Engelman and LeRoy (1995).
======================================================================
ANNEX 2
Regional patterns of land degradation
The extent of the degradation problem and its patterns
vary notably among regions:
- Africa has 25% of wasteland (the highest proportion among
regions), 12% lightly or moderately degraded and 4%
strongly or extremely degraded land (also the highest
proportion). The main type of degradation by far is the
loss of topsoil (76% of the degraded area) followed by
the loss of soil nutrients (9%). Burkina Faso, Burundi,
Ethiopia, Madagascar, Lesotho, Morocco and Rwanda are
particularly affected.
- North and Central America has 6% wasteland, 6% lightly or
moderately degraded and 1% strongly degraded land. The
main types of degradation are the loss of topsoil (75% of
the degraded area) and terrain deformation from water
erosion (16%, but 40% in Central America). Costa Rica, El
Salvador and Panama are the most affected countries.
- South America has 1% wasteland, 11% lightly or moderately
degraded and 1% strongly or extremely degraded land. The
main types of degradation are loss of topsoil from water
erosion (39% of the degraded area), loss of soil
nutrients (28%) and terrain deformation from water
erosion (12%). Brazil is particularly affected.
- Asia has 11% wasteland, 15% lightly or moderately
degraded (the highest proportion among regions) and 3%
strongly or extremely degraded land. Again the main type
is loss of topsoil (71% of the degraded area), the next
being terrain deformation (16%); salinization (7%) is
significant. China, India, Thailand and Vietnam are
particularly affected.
- Australasia has 11% wasteland, 11% lightly or moderately
degraded and a negligible proportion of strongly or
extremely degraded land. For 95%, degradation consists in
the loss of topsoil.
- Europe has a negligible proportion of wasteland, 22%
lightly or moderately degraded and 1% strongly or
extremely degraded land. The main types of degradation
are loss of topsoil from water erosion (61% of the
degraded area) and compaction (15%).
The table below quantifies the area not affected by
degradation or wasteland, as a proportion of total land area,
by region.
Proportion of total area in stable and other terrain not
degraded by human action, wasteland excluded, by region.
---------------------------------------------------------
North America...... 91% WORLD.............. 74%
South America...... 85% Asia............... 71%
Australasia........ 78% Central America.... 62%
Europe............. 77% Africa............. 59%
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Annex 3.
THE CONSEQUENCES OF EROSION
Source: FAO (1992).
=====================================================================
ANNEX. 4
LIVESTOCK & ENVIRONMENT
Livestock have been criticised for damaging the environment
in a number of ways. However, the role of livestock as agents of
environmental damage has often been misunderstood and,
consequently, misrepresented. Current independent opinion based
on research in the field presents a more balanced and positive
view of livestock and their role in sustainable agriculture in
developing countries.
CRITICISM: "Demand for pasture has resulted in
deforestation in the Amazon and Africa"
* In Africa livestock are not important components of
rainforest agricultural systems and it is rare in Africa and
elsewhere for forests to be cleared for small scale livestock
production.
* Where forest has been cleared for livestock production,
as in the Amazon, it has been by large companies responding to
financial incentives to clear forest and re-seed with pasture.
Often government and external finance has been involved and they
must carry the blame, not livestock or small scale livestock
producers.
CRITICISM: "Overgrazing in semi-arid areas destroys
vegetation and leads to desertification"
* "Livestock have been charged with wholesale devastation
of African rangelands and irreversible destruction of soils -
desertification. Heavy grazing has changed vegetative cover, but
has not seriously decreased the productivity of rangelands. The
greatest threat to this region comes from human populations and
expansion of cultivation. There is no solid evidence linking
livestock to this process."
(Winrock International Institute for Agricultural Development
Report 1992)
* "There are good scientific arguments for the case that
pastures are more productive when they are grazed low - in other
words when they appear more desert-like. Up to a point, plants
produce more new and fresh growth if they are encouraged by being
grazed, and they may be less vulnerable to drought if they are
kept small."
(Andrew Warren, University College, London. Report to U.N. 1991)
CRITICISM: "Over-stocking of pastures and concentration of cattle
around watering points accelerates soil erosion"
* The two conventional wisdoms - that on the one hand
livestock numbers have been rising for a long time, well beyond
the calculated sustainable carrying and that on the other hand the
productivity of rangelands has been falling for a long time - do
not lie at all well together."
(Ridley Nelson, senior researcher, World Bank working paper 1988)
* "The view that cattle watering points act as centres or
poles of desertification is now questioned. Only under extreme
densities of cattle is soil erosion serious. Overgrazing has been
greatly over-estimated as an environmental problem."
(Andrew Warren, University College, London. Report to U.N. 1991)
Where managed correctly the benefits of livestock to the
environment and economy greatly outweigh any potential damage.
Contributions to a healthy environment include the ability of
livestock to utilize foliage and forage that grow on marginal land
and to recycle many otherwise wasted products into high value
products.
LIVESTOCK & ENVIRONMENT
Livestock in marginal lands
Vast areas of the world are semi-arid or arid. Crop production is
extremely risky or impossible and only grasses, shrubs and trees
grow with any certainty. These provide grazing and browse to
livestock, which are the only means of survival for millions of
pastoralists.
Traditionally pastoralists established complex systems of
management which were sustainable. Given supporting services such
as marketing, it is possible for pastoralists, through their
livestock, to use arid -land vegetation and to convert it to
valuable high quality products.
Preventing erosion and adding fertility
Where rainfall is sufficient, crops and fodder trees can be
intercropped to mutual benefit. Fodder hedgerows planted on the
contour provide forage for livestock and simultaneously protect
the soil from wind and water erosion. Deep-rooted perennial
species replenish soils with minerals from lower levels while
leguminous trees provide nitrogen to soil and protein-rich feed.
Where livestock are a risk to crop land they may be confined
in stalls or yards and forage can be cut and carried to them.
Manure from enclosed livestock is a valuable and convenient source
of fertilizer.
Livestock as source of pollution
Livestock manure has been cited as a source of pollution but
accumulation of excreta and contamination of groundwater with
nitrites is primarily a problem with large-scale, intensive
livestock systems. In smallholder systems, dung is valued as a
fertilizer.
Ruminant livestock (cattle, sheep and goats) produce methane
as an end product of digestion. As a result ruminants have been
criticised for contributing to the greenhouse effect and global
warming. However, this must be seen in perspective:
* Methane from ruminant digestion forms only some 2.5% of
the total greenhouse gases: gas emissions from cars, power
stations, industries and domestic fires are much greater
* Emissions of methane from livestock have increased at a
much slower rate in recent years than emissions from direct human
activities.
* It is possible to reduce the production of methane by a
factor of 4 to 6 per unit of milk produced by feeding ruminant
animal a nutritionally balanced diet.
* Methane produced per unit of meat could be reduced by
increasing meat production from non-ruminant species.
Recycling through livestock
Feeding crop residues to livestock and using their dung as
fertilizer and soil conditioner benefits the environment directly.
Soils treated with dung have better structure, water
retention and draining capacity. As a result crops grow faster,
providing good ground cover and erosion may be reduced.
In practice, properly managed livestock have an integral
role in sustainable agricultural systems in many developing
countries.
===================================================================
ANNEX. 5
Machakos: A Qualified Success Story
With effort, farmland can be conserved and even improved as
local population grows rapidly. This is the lesson offered by the
1.4 million-hectare Machakos district near Nairobi in Kenya. What
is not clear, however, is that such conservation successes can be
sustained indefinitely as populations continue to grow.
A region of steeply sloping land that receives rare and
erratic rainfall, Machakos was first settled by the Akamba people
in the early part of the 20th century. By the 1930s, it had been
severely degraded by overuse, with less than 5 per cent tree cover
and soil erosion visible in 75 per cent of the inhabited area.
Some observers predicted ecological collapse. Instead, the
reverse happened. Over the next six decades, the population of
Machakos expanded almost six-fold, to 1.4 million. Yet soil
erosion decreased, tree cover increased, and the district moved
closer to self-sufficiency in food. More people were talking
better care of scarce, and therefore precious, land, even as they
coaxed more production out of each hectare.
Surprisingly high population densities may be compatible
with sustainable land use under certain conditions. Within
Machakos, many farmers were able to diversify their income by
finding non-farm jobs, applying the additional income to land
conservation. Education, land tenure, community-government
partnerships and prominent leadership roles for women also
enhanced conservation efforts.64 But this does not support the
idea that population growth per se is good for land. The
diversity of natural vegetation and wildlife in Machakos has
declined, and local soils may also be deteriorating in quality,
although only limited data is available.
Key natural thresholds may eventually be exceeded in
Machakos. The fact that yields and some indicators of soil
quality improved between 1930 and 1990, despite the rapid
population growth, demonstrates the capacities of committed and
resourceful farmers. Yet this experience hardly suggests the
district's human population could increase sixfold yet again and
still improve yields and reduce soil erosion. Finding the balance
between people and land remains a critical task.