and increases the availability of fresh water for drinking and household consumption. upa can help to preserve bioregional ecologies from being transformed into cropland. urban agriculture saves energy (e.g. energy consumed in transporting food from rural to urban areas). local production of food also allows savings in transportation costs, storage, and in product loss, what results in food cost reduction. upa improves the quality of the urban environment through greening and thus, a reduction in pollution. urban agriculture also makes the city a healthier place to live by improving the quality of the environment. upa is a very effective tool to fight against hunger and malnutrition since it facilitates the access to food by an impoverished sector of the urban population. poverty alleviation: it is known that a large part of the people involved in urban agriculture is the urban poor. in developing countries, the majority of urban agricultural production is for self-consumption, with surpluses being sold in the market. according to the fao (food and agriculture organization of the united nations), urban poor consumers spend 60–80% of their income on food, making them very vulnerable to higher food prices. upa provides food and creates savings in household expenditure on consumables, thus increasing the amount of income allocated to other uses. upa surpluses can be sold in local markets, generating more income for the urban poor. community centers and gardens educate the community to see agriculture as an integral part of urban life. the florida house institute for sustainable development in sarasota, florida, serves as a public community and education center in which innovators with sustainable, energy-saving ideas can implement and test them. community centers like florida house provide urban areas with a central location to learn about urban agriculture and to begin to integrate agriculture with the urban lifestyle. urban farms also are a proven effective educational tool to teach kids about healthy eating and meaningful physical activity. trade-offs space is at a premium in cities and is accordingly expensive and difficult to secure. the utilization of untreated wastewater for urban agricultural irrigation can facilitate the spread of waterborne diseases among the human population. although studies have demonstrated improved air quality in urban areas related to the proliferation of urban gardens, it has also been shown that increasing urban pollution (related specifically to a sharp rise in the number of automobiles on the road), has led to an increase in insect pests, which consume plants produced by urban agriculture. it is believed that changes to the physical structure of the plants themselves, which have been correlated to increased levels of air pollution, increase plants' palatability to insect pests. reduced yields within urban gardens decreases the amount of food available for human consumption. studies indicate that the nutritional quality of wheat suffers when urban wheat plants are exposed to high nitrogen dioxide and sulfur dioxide concentrations. this problem is particularly acute in the developing world, where outdoor concentrations of sulfur dioxide are high and large percentages of the population rely upon urban agriculture as a primary source of food. these studies have implications for the nutritional quality of other staple crops that are grown in urban settings. agricultural activities on land that is contaminated (with such metals as lead) pose potential risks to human health. these risks are associated both with working directly on contaminated land and with consuming food that was grown in contaminated soil. municipal greening policy goals can pose conflicts. for example, policies promoting urban tree canopy are not sympathetic to vegetable gardening because of the deep shade cast by trees. however, some municipalities like portland, oregon, and davenport, iowa are encouraging the implementation of fruit-bearing trees (as street trees or as park orchards) to meet both greening and food production goals.