In 2011, the world's population was more than 7
billion. And half of these lived in towns.
In 2030, according United Nations, we’ll be 5 billion urban (over 8.3
billion on earth). So nearly 1.5 billion of additional urban people will stay
in towns within two decades.
Forecasts of a research published on September 18 in
Proceedings of the National Academy of Sciences (PNAS) of USA reveal that if
current trends in population density continue and all areas with high
probabilities of urban expansion, then by 2030, urban land cover will increase
by 1.2 million km2, nearly tripling the global urban land area circa 2000. Half
of this expansion will be in Asia, mainly in China
and India.
However, it is in Africa where the highest rates forecasted urban growth will
take place with an increase of 590% between 2000 and 2030, mainly around the Nile River
in Egypt, North of Nigeria, Guinea and North of Victoria Lake and too in Addis Ababa region, in Ethiopia.
That will have many environmental impacts: the deforestation
decreasing the carbon pool with more CO2 emissions for land use change.
Biodiversity will also be affected as magnifying
cities nibble on the habitats of the animals. Geographic modelling published in
the PNAS shows as well that urban territory gain by man will put at risk
habitat of some two hundred species of amphibians, of mammals and birds already
listed as endangered or endangered critic extinction
The authors point out that their study does not take
into account what they call indirect urbanization, to say impact of settlements
on their hinterlands: wood supply, agricultural raw materials, deduction in
water, burying waste in rural areas, etc. Moreover, consumption of meat of
urban population is being greater than that of the rural; so one can expect an
increased demand for meat products, with all that implies for feeding the animals,
the production of methane by herds, the treatment of manure... Urbanization is
therefore far from influence only on spaces where city takes up residence. Other
studies should evaluate these cascading effects on a large scale.
In the meantime, the mass urbanisation phenomenon is
in an acceleration phase. These are hundreds of billions of dollars that are
invested every year in infrastructures, whether for buildings, pathways of
communication, and networks of water, gas, power and telecommunications. And
when the concrete is poured or the macadam spread, for a long time. To mitigate
global impact of the billion and a half additional urban persons that will
happen by the year 2030, the authors of the PNAS article suggests priority on
the densification of cities rather than their spread. For them, the compact
development, in addition to maximally preserve natural areas, presents benefits
and reduce energy losses. But the responsible of arrangement of the territory
of each region or each country must think quickly because, if they want to
limit impact of cities on the environment, response time will be very
short. Although urbanization is often
considered a local issue, the aggregate global impacts of projected urban
expansion will require significant policy changes to affect future growth
trajectories to minimize global biodiversity and vegetation carbon losses,
according the authors.
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