IMPACTS ON HUMAN SYSTEMS

URBAN HEAT ISLANDS

An urban heat island, or UHI, is a metropolitan area that's a lot warmer than the rural areas surrounding it. Heat is created by energy from all the people, cars, buses, and trains in big cities.

The progressive replacement of natural surfaces through urbanization, constitutes the main cause of UHI formation. Natural surfaces are often composed of vegetation and moisture-trapping soils. Therefore, they utilize a relatively large proportion of the absorbed radiation in the evapotranspiration process and release water vapour that contributes to cool the air in their vicinity. In contrast, built surfaces are composed of a high percentage of non-reflective and water-resistant construction materials. As consequence, they tend to absorb a significant proportion of the incident radiation, which is released as heat.

Elevated temperatures from urban heat islands, particularly during the summer, can affect a community’s environment and quality of life and there are some important impacts:

Increased Energy Consumption 
Elevated summertime temperatures in cities increase energy demand for cooling.
 
Elevated Emissions of Air Pollutants and Greenhouse Gases  
As described above, urban heat islands raise demand for electrical energy in summer. Companies that supply electricity typically rely on fossil fuel power plants to meet much of this demand, which in turn leads to an increase in air pollutant and greenhouse gas emissions.
 
Compromised Human Health and Comfort 
Increased daytime temperatures, reduced nighttime cooling, and higher air pollution levels associated with urban heat islands can affect human health by contributing to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.


http://www.nasa.gov/topics/earth/features/heat-island-sprawl.html
http://earthobservatory.nasa.gov/IOTD/view.php?id=36227



FOOD SECURITY
 

Changes in climatic conditions have affected the production of crops. Higher temperatures will have an impact on yields while changes in rainfall could affect both crop quality and quantity.

 

The three mos important crops are mize, rice and wheat and they are challenged by pathogens that threaten our food security, specially fungi. The spores of some fungi come through the air and attack leaves, making dead spots or even killing the whole leaf. Some fungi live in the soil and enter roots. They can either block the water-conducting cells or kill them, causing the plant to wilt. In many cases the plants is seriously damaged or may even die.

The loss of crop causes losses of millions of dollars annually and the attack of the fungi can result a the situation where we could only feed 38% of today's population. Fortunately, scientists are looking the way of increasing the resistance of crops to disease and other who are looking for more robust anti-pathogen and anti-pest strategies for future.