AFRICA ENVIRONMENT OUTLOOK
Past, present and future perspectives

QUANTITATIVE EXPRESSIONS OF THE SCENARIOS

The generation of quantitative expressions for the different scenarios requires the use of models, or input from experts. The applications described in this work were developed at the regional scale, and were organized with the help of the SEI’s PoleStar software system. The goal of the PoleStar project is to give operational meaning to the notion of sustainable development, a challenging task which requires a broad view—across issues, over a range of spatial scales and over long timescales. The PoleStar software system has been applied at the global level by the SEI for UNEP’s GEO-3 report, and also for the scenarios of the GSG. Scenario development in the AEO benefited from the good assemblage of data undertaken by the SEI, but has been modified in different ways. Some of the major driving variables—Gross Domestic Product (GDP), population and urban population—differ from those of the GEO-3 report or the GSG scenarios. In part, this reflects an update of the data for Africa, using more recent information published in Cities in a Globalizing World (UNCHS 2001).

For illustrative purposes, six possible outputs are examined, which represent the four dimensions of: demographics; economy and society; agriculture and forestry; and environment. The demographic dimensions consist of the total population and the urban population figures for Africa, and for each of its sub-regions. The economy and society dimension consists of the GDP measured at the purchasing power parity rates, with 1995 as base. The third dimension, agriculture and forestry, consists of severely degraded cropland. The environment dimension consists of water use and urban household water pollution. The quantitative expressions of the scenarios for these variables are presented as Figures 4.5, 4.6, 4.7, 4.8, 4.9 and 4.10.

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Figure 4.5: Populations in the Scenarios and by Sub-regions

UNEP 2002

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Figure 4.6: Urban populations in the Scenarios and by Sub-regions

UNEP 2002

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Figure 4.7: GDP (Purchasing Power Parity (PPP)) in the Scenarios and by Sub-regions

UNEP 2002

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Figure 4.8: Severely degraded croplands in the Scenarios and by Sub-regions

UNEP 2002

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Figure 4.9: Water use in the Scenarios and by Sub-regions

UNEP 2002

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Figure 4.10: Urban household water pollution in the Scenarios and by Sub-regions

UNEP 2002

Populations grow at mid-range levels in the Market Forces scenario. The spread of education for women, poverty-reduction programmes and widespread use of birth-control methods leads to a significant slowing in population growth rates in the Policy Reform scenario, and there is a radical reduction in growth rates in the Great Transitions scenario. In the Fortress World scenario, social collapse, poverty and the failure of educational systems precipitate a massive expansion of the population, reaching, in 2032, four times the population in 1995.

Urban populations follow similar trends to population as a whole. However, the differences between the Fortress World scenario and the Great Transitions scenario are even more pronounced. Widespread alternatives to urban and periurban settlement expansion in the Great Transitions scenario lead a barely perceptible growth in total urban population. In the Fortress World scenario, the loss of farmland to élite interests, land degradation and the collapse of urban markets for rural agricultural produce drives billions of people toward the already overcrowded cities.

Patterns of GDP growth are nearly the inverse of the patterns of population growth. Growth in the Market Forces scenario is rather robust compared to recent experience in the region, but it is slow compared to other developing regions as the new millennium begins to unfold. In the Policy Reform scenario, the gap is much smaller, because several African countries see rapid growth in GDP. The collapse in society, polity and infrastructure in the Fortress World scenario underlies very sluggish growth in per capita income, which grows just barely over the rate of population growth over the scenario period. In the Great Transition scenario, with an international environment that is focusing on equity through more vigorous connections with other southern regions and in a supportive domestic environment, output per person expands rapidly, reaching an average level for the region as a whole that is close to the average of the industrialized countries in 1995.

Cropland degradation rates are highest in the Market Forces scenario and the Fortress World scenario, and the amount of cropland degraded adds to the total that must be converted from other land-use types.

Water use grows under each of the scenarios, as populations expand and incomes grow. In the Policy Reform scenario and the Great Transitions scenario, especially, rising demand for water-intensive end uses is offset by greater efficiency. However, despite relatively greater improvements in water efficiency in the Great Transitions scenario compared to the Policy Reform scenario, the rapid economic growth in the Great Transitions scenario leads to comparable levels of water withdrawals. At the same time, water-use intensity remains well below that of the industrialized regions. In the Fortress World scenario, relatively modest water withdrawals—below those of any of the other scenarios—hide a disturbing picture of collapsing waterdelivery infrastructure and degraded water sources, leading to severe water shortages and declines in the population with access to clean water.

Total water pollution from urban households depends on both the size of the urban population and the water-treatment infrastructure. The high average incomes in the Policy Reform scenario and the Great Transitions scenario, combined with low urban populations, lead to very low total water pollution loadings. In the Great Transitions scenario, urban water pollution falls after 2015, as urban population levels off and treatment continues to improve. The poor infrastructure and rapid urban population growth in the Fortress World scenario leads to a massive increase in total water pollutant loadings from urban households.