Much good agricultural land is threatened by
chemical pollution, particularly - as here in China - by waste products
from urban centres. Chemical degradation is responsible for 12 per
cent of global soil degradation
Source: UNEP, Zehng Zhong Su, China, Still Pictures
Urban areas occupy only 1 per cent of the Earth's
land area (UNEP 2000). However, urban expansion, including land requirements
for industry, transport and for leisure activities in all regions, increases
pressures on land resources. In the United States, for example, about
400 000 ha of farmland are lost to urbanization annually and China lost
about 5 million ha of farmland to towns and cities during 1987-92 (UNFPA
2001). Land degradation, river siltation and soil pollution, from acid
rain and industrial wastes, are some of the environmental issues associated
with urbanization and industrialization.
The waste generated by cities is a major source of degradation. It is
estimated that about 1.95 million ha of land have been degraded by industry
and urbanization (FAO 1996). One cause has been the export by some developed
countries of hazardous and toxic wastes to developing regions.
The international response to this was the 1989 Basel Convention on the
Control of Transboundary Movements of Hazardous Wastes and their Disposal.
The Basel Convention, which entered into force in 1992 (see Chapter 1), aims to reduce transboundary movements of hazardous wastes, minimize
the creation of such wastes, and prohibit their shipment to countries
lacking the capacity to dispose of hazardous wastes in an environmentally
Urbanization has also spawned urban agriculture (see 'Urban
areas'), which was hardly recognized internationally in the 1970s
but has been expanding globally over the past 15-20 years, 'more rapidly
than urban populations, and in many countries more rapidly than their
economies' (Smit 1996). Urban agriculture takes place on both public and
private land, both legally and illegally. More than 800 million urban
dwellers were involved in urban agriculture in 1993 (Smit 1996). For example,
in the Brazilian city of São Paulo, agriculture is a major planned land
use in the city's metropolitan master plan, which was adopted in the 1990s.
In virtually all regions, urban agriculture has become one of the major
food-producing activities. For example, most households in the Southeast
Asia and Pacific Island sub-regions practise urban agriculture (Sommers
and Smit 1994). About 30 per cent of the Russian Federation's food is
produced on 3 per cent of the land in suburban dachas (Sommers and Smit
1994). In Moscow, families engaged in agriculture grew from 20 per cent
of the city's population in 1970 to 65 per cent in 1990 (Smit 1996). During
1980-90, urban agriculture in the United States grew by 17 per cent (Smit
1996). In some African urban areas, the response by municipal authorities
has been to cut down the crops to enforce land-use by-laws.
|Chemicals and land use
Important recent developments include:
- The Stockholm Convention on Persistent Organic Pollutants (POPs)
was adopted in May 2001 (see Chapter 1).
- UNEP, together with FAO and WHO, is promoting more sustainable
practices in replacing POP pesticides with integrated pest management.
The Global Crop Protection Federation is playing a proactive role
in promoting the judicious use of pesticides and the prevention
of toxic exposures and misuse of pesticides.
Other actions include pilot projects to demonstrate the technical
and economic feasibility of new technologies to destroy obsolete
chemicals and pesticides; and the encouragement of donors and industry
to increase funding for management and disposal of these substances.
The impacts of urban agriculture include air, water and soil pollution,
mainly from improper use of chemicals. Advocates of urban agriculture
argue that, in addition to providing food, the activity can contribute
to improving the environment through recycling organic matter. Solid wastes
can be composted and used to fertilize soils.
|Urban agriculture in Zimbabwe
In Harare, Zimbabwe, sanctions on urban agriculture were lifted
temporarily in 1992. Within two years, the area cultivated had doubled
and the number of farmers more than doubled. Municipal costs for
landscape maintenance and waste management were down, food prices
were down, and hundreds of jobs had been created. Several benefits
were gained from just a change in policy. Similar policyrelated
benefits were documented in Lusaka and Accra in the 1970s (Smit