Environmental Engineering Reference
In-Depth Information
urbanized territories from year 1970 to 2000 amount to about 58,000 km
2
. India,
China, and Africa have experienced the highest rates of urban land expansion,
while the largest change in total urban space has occurred in North America. It is
expected that, by the year 2030, the urban expansion will account for about 1.5
million km
2
, an area as large as Mongolia.
1
The results of the study reveal that in
several Countries the variations of the urban expansion rate correlate to the degree
of household income, to the socio-economic situations in the nations and regions
in addition to the political situation.
This rapid and intensive urbanization is the most impressive and irreversible
landscape reshaping made by man, which undoubtedly will cause environmental
changes and global warming. Not to mention the destruction of the ecosystems and
of coastal territories, rivers, agricultural lands, forests, savannas and natural habitat
areas that are extremely vulnerable and very valuable.
Throughout the world, like in Europe
2
, both large megalopolis and small towns
are the places where the majority of the population prefer living in because cities
are thought to be special and exclusive places, the heart of national and global
socio-economic systems. The most competitive cities are characterized by popu-
lation growth, availability of employment positions, but also by the ability to
attract financial, political and cultural activities as well as traffic congestion.
Nevertheless, cities are high energy-consuming places, in fact, they use about
75 % of the world energy supply and contribute significantly to the greenhouse gas
emissions (80 % of the gas emissions of CO
2
), entailing high economic costs like
consumption of soil, water and energy, pollution, inefficiency of the productive
structures and services, shortage of housing, urban decay). Moreover, cities are
characterized by serious social disadvantages like high unemployment rates, job
insecurities and social marginalization, spatial segregation, poverty, crime, migration.
Cities, in the other parts of the world, are built following the models, archi-
tecture and shape of western cities that, at international level, are considered
models of modern culture, but plagued by an unsustainable growth rate and the
need of considerable amount of resources.
Cities have a very important role in climate change because negative effects are
considerably greater, and global problems are amplified when combined with local
phenomena (microclimate, pollution, etc.). This combination creates events like
the ''heat island''.
The layout of the city greatly influences the urban microclimate because of
extensive overbuilding, decreasing in agricultural areas, soil sealing, expansion of
paved areas compared to green spaces. Moreover, physical structure, urban areas
1
Analysis has been developed by K. C. Seto, M. Fragkias, B. Güneralp, M. K. Reilly. The study
represents the first estimate of how urban areas are growing globally and how they can grow in
the future. Results show considerable variation in the rates of urban expansion over the study
period, with the highest rates in China followed closely by Southwest Asia. Average rates of
urban expansion are lowest for Europe, North America, and Oceania.
2
The 73 % of Europe population lives in urban areas, produces around 80 % of GDP and
consumes up to 70 % of the energy.
