Environmental Engineering Reference
In-Depth Information
Pests and Disease
Changes in climate can affect the spread of illness and diseases such as
malaria and West Nile Virus, carried by animal hosts and mosquito, midge,
fly, or tick vectors. Increasing temperatures and changes in precipitation
patterns can accelerate current trends of increased risk of exposure to dis-
ease by expanding the geographic range and/or populations of the vectors
(Ogden et al., 2008). In addition to the potential for more vectors to be
present, warmer temperatures increase the virus replication rate, increasing
the efficiency of virus transmission (Mellor, 2000).
Despite initial projections suggesting the potential for dramatic future
increases in the geographic range of malaria and other infectious diseases
under climate change (e.g., Martin and Lefebvre, 1995), subsequent stud-
ies have highlighted how the complexity of the systems—involving viral,
bacterial, plant, and animal physiology, as well as sensitivity to changes in
climate extremes, including precipitation intensity and temperature variabil-
ity—challenges attempts to resolve the influence of historical climate change
on observed trends in disease incidence and develop future projections
specific to any particular level of global temperature change. This is even
true for what many previously considered the poster child for the influence
of climate change on infectious diseases, the spread of malaria throughout
the East African highlands (e.g., Pascual et al., 2006).
If historical contributions are difficult to resolve, prediction of future
trends is even more so. Most recent projections suggest that the ranges of
malaria and other diseases may shift, but increases in some areas will likely
be balanced out by decreases in others, resulting in little net increase in
area (Lafferty, 2009). The potential for genetic mutation, the influence of
changing agricultural techniques, and increased transportation and trade
between regions previously not in regular contact are all confounding fac-
tors that have been cited as complicating the influence of climate change
on a given disease (Gould and Higgs, 2009).
It is also important to remember that good sanitation and insect control
programs can limit disease spread even under suitable climate conditions
(Lafferty, 2009). In 1882, malaria in the continental United States extended
from the Gulf of Mexico to Minnesota. Draining of swamps, improved
pesticides, and better management of water resources contributed to the
eradication of malaria in the United States shortly after World War II (Oaks
et al., 1991). Replicating methods proven successful in the past may be one
way to reduce the risk associated with climate change and vector-borne
disease.
