that the presence of trees are "highly responsive to changes in [neighborhood] income." Low-income neighborhoods tend to have significantly fewer trees than neighborhoods with higher incomes. They described this unequal distribution of trees as a demand for "luxury," rather than "necessity." According to the study, "for every 1 percent increase in per capita income, demand for forest cover increased by 1.76 percent. But when income dropped by the same amount, demand decreased by 1.26 percent." Trees are a necessary feature in combating most of the urban heat island effect because they reduce air temperatures by , and surface temperatures by up to . Researchers hypothesized that less-well-off neighborhoods do not have the financial resources to plant and maintain trees. Affluent neighborhoods can afford more trees, on "both public and private property." Part of this is also that wealthier homeowners and communities can afford more land, which can be kept open as green space, whereas poorer ones are often rentals, where landowners try to maximize their profit by putting as much density as possible on their land. Inequality of impervious surfaces Researchers have also noted that the spread of impervious surfaces is correlated with low socioeconomic status neighborhoods across various U.S. cities and states. The presence of these materials, which include concrete, tar and asphalt, serves as a predictor of "intra-urban variation in temperature." In 2013, Jesdale et al. found that after adjusting for ecoregions, precipitation patterns, and segregation patterns, the greatest racial/ethnic disparity in the distribution of heat risk-related land cover characteristics was between blacks and whites, suggesting an issue of environmental health equity. Impact on nearby water bodies UHIs also impair water quality. Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes. Additionally, increased urban water body temperatures lead to a decrease in diversity in the water. In August 2001, rains over Cedar Rapids, Iowa, led to a 10.5C (18.9F) rise in the nearby stream within one hour, which led to a fish kill. Since the temperature of the rain was comparatively cool, it could be attributed to the hot pavement of the city. Similar events have been documented across the American Midwest, as well as Oregon and California. Rapid temperature changes can be stressful to aquatic ecosystems. Permeable pavements may mitigate these effects by percolating water