Urbanization leads to rural migration and suburban concentration into cities. As cities grow, more land and waterways are modified to accommodate increased population needs. This modification impacts local ecosystems and drives changes in biogeochemical cycles. For example, fertilizer runoff from agricultural lands pollutes waterways and causes eutrophication. Urban areas also impact the climate through increased greenhouse gas emissions and the urban heat island effect. Understanding these environmental effects of urbanization is important for sustainable future development.

2. URBANISATON
Urbanisation is the physical growth of urban areas which result in rural
migration and even suburban concentration into cities, particularly the very
large ones.
Urbanization occurs as individual, commercial, and governmental efforts reduce
time and expense in commuting and transportation and improve opportunities
for jobs, education, housing, and transportation.
The phenomenon of Urban heat islands has become a growing concern. An
urban heat island is formed when industrial and urban areas are developed
resulting in greater production and retention of heat.
In cities, where there is less vegetation and exposed soil, the majority of the
sun’s energy is absorbed by urban structures and asphalt.
Vehicles and factories release additional city heat, as do industrial and domestic
heating and cooling units.

3. URBAN ECOLOGY
Urban Ecology is the scientific study of the relation of living organisms with each
Other and their surroundings in context of the proposed urban environment.
The urban environment refers to environments dominated by high density residential
And commercial buildings, paved surfaces, and other intense human influences, which
create a unique landscape dissimilar to many previously studied environments in the
field of ecology.

4. EFFECTS ON THE ENVIRONMENT
Humans are the driving force behind the urban ecology and influence the
environment in a variety of ways, such as modifying land surface and waterways .
MODIFICATION OF LAND AND WATERWAYS
High demand of land not only to build urban centres, but also to build surrounding
Suburban areas for housing.
Land is also allocated for agriculture to sustain the growing population of the city.
This necessitate corresponding deforestation to meet the land-use and resource
Requirements of urbanisation.

5. Along with manipulation of land to suit human needs, natural water resources
such as rivers and streams are also modified in urban establishments.
Modification can come in the form of dams, artificial canals, and even the reversal
Of rivers.
Urban areas in natural desert settings often bring in water to maintain human
Population and will likely have effects on the local desert climate.
Modification of aquatic systems in urban areas also results in decreased stream
Diversity and increased pollution.

8. IMPACT OF BIOGEOCHEMICAL
PATHWAYS IN THE URBAN
LANDSCAPE
Urbanization results in a large demand for chemical use by industry, construction,
agriculture, and energy providing services.
Such demands have a substantial impact on biogeochemical cycles, resulting in
phenomena such as acid rain, eutrophication, and global warming.
Demand for fertilizers to meet agricultural needs exerted by expanding urban
centres can alter chemical composition of soil.

9. Nitrogen and phosphorus used in fertilizers have caused severe problems in the form
of agricultural runoff, which alters the concentration of these compounds in local rivers
and streams, often resulting in adverse effects on native species.
Effect of agricultural runoff is the phenomenon of eutrophication.
When the fertilizer chemicals from agricultural runoff reach the ocean,
an algal bloom results, then rapidly dies off.
The dead algae biomass is decomposed by bacteria that also consume large quantities
of oxygen, which they obtain from the water, creating a ‘dead zone’ without oxygen
for fish or other organisms.
For example - the dead zone in the Gulf of Mexico .
Just as pollutants and alterations in the biogeochemical cycle alter river and ocean
ecosystems, they exert likewise effects in the air.
Smog stems from the accumulation of chemicals and pollution and often manifests
in urban settings, which has a great impact on local plants and animals.

10. IMPACT ON CLIMATE
Urban environments and outlying areas have been found to exhibit unique
local temperatures, precipitation, and other characteristic activity due to a
variety of factors such as pollution and altered geochemical cycles.
The urban effects on climate are –
Urban Heat Island,
or Oasis Effect,
Green House Gases, And
Acid Rain.

11. URBAN HEAT ISLAND/ OASIS EFFECT
The urban heat island is a phenomenon in which central regions of urban
centres exhibit higher mean temperatures than surrounding urban areas.
The reflecting power of a surface, and the increased surface area of buildings
to absorb solar radiation.
Concrete, cement, and metal surfaces in urban areas tend to absorb heat
energy rather than reflect it, contributing to higher urban temperatures.
The heat island effect has corresponding ecological consequences on resident
species.
Cities in desert environments show a different trend known as the “urban
oasis effect”.

14. GREENHOUSE GASES
Greenhouse gas emissions include those of carbon dioxide and methane
from the combustion of fossil fuels to supply energy needed by vast urban
metropolises.
Other greenhouse gases include water vapour, nitrous oxide, and ozone.
Increases in greenhouse gases due to urban transport, construction,
industry and other demands have been correlated strongly with increase in
temperature.
Sources of methane are agricultural dairy cows and landfills.

17. ACID RAIN AND POLLUTION
Processes related to urban areas result in the emission of numerous
pollutants, which change corresponding nutrient cycles of carbon, sulphur,
nitrogen, and other elements.
Ecosystems in and around the urban centre are especially influenced by
these point sources of pollution.
High sulphur dioxide concentrations resulting from the industrial demands
of urbanization cause rainwater to become more acidic.
Such an effect has been found to have a significant influence on locally
affected populations, especially in aquatic environments.
Wastes from urban centres, especially large urban centres in developed
nations, can drive biogeochemical cycles on a global scale.

19. Urbanization results in a series of both local and far-reaching
effects on biodiversity, biogeochemical cycles, hydrology, and
climate, among many other stresses.
Urbanisation is causing the loss of greenery.
Urbanization continues to increase exponentially around the
world.
Understanding its effects on the environment is vital for safe
and productive development in the future.
CONCLUSION