User:VillanuevaL/Effects of climate change on human health

Drought
Arguably one of the worst effects that drought has directly on human health is the destruction of food supply. Farmers who depend on weather to water their crops lose tons of crops per year due to drought. Plant growth is severely stunted without adequate water, and plant resistance mechanisms to fungi and insects weaken like human immune systems. The expression of genes is altered by increased temperatures, which can also affect a plant's resistance mechanisms. One example is wheat, which has the ability to express genes that make it resistant to leaf and stem rusts, and to the Hessian fly; its resistance declines with increasing temperatures. A number of other factors associated with lack of water may actually attract pestilent insects, as well- some studies have shown that many insects are attracted to yellow hues, including the yellowing leaves of drought-stressed plants. During times of mild drought is when conditions are most suitable to insect infestation in crops; once the plants become too weakened, they lack the nutrients necessary to keep the insects healthy. This means that even a relatively short, mild drought may cause enormous damage- even though the drought on its own may not be enough to kill a significant portion of the crops, once the plants become weakened, they are at higher risk of becoming infested.

The results of the loss of crop yields affect everyone, but they can be felt most by the poorest people in the world. As supplies of corn, flour and vegetables decline, world food prices are driven up. Malnutrition rates in poor areas of the world skyrocket, and with this, dozens of associated diseases and health problems. Immune function decreases, so mortality rates due to infectious and other diseases climb. For those whose incomes were affected by droughts (namely agriculturalists and pastoralists), and for those who can barely afford the increased food prices, the cost to see a doctor or visit a clinic can simply be out of reach. Without treatment, some of these diseases can hinder one's ability to work, decreasing future opportunities for income and perpetuating the vicious cycle of poverty.

While drought does indeed greatly impact agricultural production, it also has a large impact on naturally occurring vegetation. The potential exists for climate change and variability to have a major impact on the frequency of severe droughts. With the increase in frequency of droughts will come conditions more prime for wildfires. Given the current climate change trends, fire seasons are expected to become longer, fire weather is expected to become more severe, and the area burned and amount of fires will increase. This in turn can lead to a greater risk of flooding due to higher runoff occurring from the removal of potential interception and transpiration from the hydrologic cycle.

Floods
Health concerns around the world can be linked to floods. Short term implications include mortalities, injuries and diseases, while long term implications include non-communicable diseases and psychosocial health effects. With the increase in temperatures worldwide due to climate change, extreme precipitation events are projected to increase, and this may lead to more severe flooding. It has been determined that climate change and variability have the potential to drastically impact human exposure to flood hazards, but this comes with a lot of uncertainty due to multiple climate models. Similar to droughts, climate change has also been shown to have the potential to increase the frequency of bigger storm events. This increase in the frequency of large storm events would alter existing Intensity-Duration-Frequency curves (IDF curves) due to the change in frequency, but also by lifting and steepening the curves in the future. The use of intensity-duration-frequency curves requires the assumption that the past will be representative of future conditions. However, in the field of hydrology, stationarity may no longer be a good assumption due to the rapid changes from climate change.