About UNEP UNEP Offices News Centre Publications Events Awards Milestones UNEP Store
GEO Year Book 2004/5  
UNEP Website GEO Home Page
Changing human and natural populations
Figure 2: Contribution of urban and rural population growth to total population growth 1950–2030
Source: UNDESA 2004

The latest revision of the United Nations Population Division's World Urbanization Prospects, published in 2004, reveals an increasingly urban future. By 2007, for the first time in human history, the urban population will form more than half of the total. Almost all population growth in the next 30 years will be concentrated in urban areas, and most of this growth will occur in less developed countries. The rural population will decline between 2003 and 2030, from 3.3 billion to 3.2 billion, so that the share of growth due to rural populations (as well as to the populations of some developed countries) will be actually negative (Figure 2) (UNDESA 2004).

According to UN-HABITAT: "if nothing is done to check the current trend, the number of people living in slums will rise from one billion today to some 1. 5 billion by the year 2020. " This will make it difficult to achieve the Millennium Development target of significantly improving the lives of at least 100 million slum-dwellers by 2020 (UN-HABITAT 2004).

While the international community has pledged to achieve by 2010 a significant reduction of the current rate of biodiversity loss at the global, regional and national level (CBD 2004a), studies provided new indications that biodiversity loss is increasing.

Amphibians are declining at an unprecedented rate. Their permeable skin makes them particularly vulnerable to pollution and climate change, so they serve as a good indicator of environmental health. The Global Amphibian Assessment found that just under one third of the world's 5 743 amphibian species are threatened with extinction (Figure 3). This is considerably higher than the comparable figures for birds (12 per cent) and mammals (20 per cent), the only other groups for which comprehensive assessments have been completed (see GEO Indicators section). At least nine amphibian species have gone extinct since 1980. Another 113 species have not been reported from the wild in recent years and are considered to be possibly extinct (GAA 2004). Some 43 per cent of all amphibian species are in population decline, while fewer than one per cent are increasing (Stuart and others 2004).

Figure 3: Global status of amphibians
Source: GAA 2004
Box 1: Human appropriation of Net Primary Production
Human appropriation of net primary production (NPP), as a per cent of total NPP. The local consumption rate of NPP is compared to the local production rate of NPP. Highly populated areas (yellow and red) consume up to 300 times their local production.
Source: Imhoff and others 2004

A new assessment based on satellite and statisticaldata found that, globally, humans are already consuming 20 per cent of Earth's total net primary production (NPP) on land (Imhoff and others 2004). NPP is the amount of plant material generated through photosynthesis that remains after respiration. The study calculated the amount of NPP required to produce all the land-based products consumed in the base-year 1995, including plant foods, meat and dairy, natural fibres and wood-based products.

The balance between supply of and demand for NPP varies considerably on a geographic basis (see figure). Western Europe and South Central Asia consume the equivalent of more than 70 per cent of their regional NPP supply, while East Asia consumes 63 per cent. Human use of NPP in other regions is much lower, ranging from 24 per cent in North America down to only 12 per cent in Africa and 6 per cent in South America (see table). At more local scales, spatial differences are even more striking, ranging from over 30 000 per cent of local NPP in large urban centers down to almost nothing in sparsely populated areas. This share is likely to rise as human demands for food, fibre and fuel grow.

Human-appropriated net primary production (NPP) of selected regions (intermediate estimate) calculated on a per capita basis.

Region

Area
(million km2)

Population
(millions)

NPP supply
(‘000 million
tonnes)

Human appropriation
of NPP (‘000
million tonnes)

Human
appropriation
(as % of regional NPP)

Human appropriation per capita (tonnes)

Africa
31.1
742
12.50
1.55
12.4
2.08
East Asia
11.9
1400
3.02
1.91
63.3
1.37
South-Central Asia
10.9
1360
2.04
1.64
80.4
1.21
Western Europe
1.2
181
0.72
0 52
72.2
2.86
North America
19.7
293
6.67
1.58
23.7
5.40
South America
18.4
316
16.10
0.98
6.1
3.11
Source: Imhoff and others 2004

Earthprint.com Order the Book