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Effects of deforestation

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Deforestation of the African Highland

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The Ethiopian Highlands

Environmental changes such as deforestation could increase local temperatures in the highlands thus could enhance the vectorial capacity of the anopheles.[1] Anopheles mosquitos are responsible for the transmission of a number of diseases in the world, such as, malaria, lymphatic filariasis and viruses that can cause such ailments like O'nyong'nyong virus.[1] Environmental changes, climate variability, and climate change are such factors that could affect biology and ecology of Anophelse vectors and their disease transmission potential.[1] Climate change is expected to lead to latitudinal and altitudinal temperature increases. Further global warming projections indicate that the best estimate of surface air warming for a “high scenario” is 4 C, with a likely range of 2.4-6.4 C by 2100.[2] A temperature increase of this size would alter the biology and the ecology of many mosquito vectors and the dynamics of the diseases they transmit eg Malaria. Arthropods critically depend on ambient temperature for survival and development,[3] their distribution range is limited by the temperature. Climate warming or any factor that alters the microclimate conditions of Anopheles mosquitos (e.g., Deforestation) in the highlands may facilitate the persistence of the mosquito population. [4] Climate warming can mediate mosquito physiology and metabolic rate because metabolic rate increases exponentially rather than linearly with temperature ectotherms.[5] Anopheles mosquitoes in highland areas are to experience a larger shift in their metabolic rate due to the climate change. This climate change is due to the deforestation in the highland areas where these mosquitos dwell. When temperature rises, the larvae take a shorter time to mature [6] and, consequently, there is a greater capacity to produce more offspring. The Changes in the microclimatic conditions in the human residences induced by deforestation significantly shortened the duration of the mosquitoes' gonotrophic cycle by 1.7 days (4.6 vs 2.9 days)[7] The gonotrophic cycle is the period between the taking of a blood meal by a mosquito, including the digestion of the blood meal, until oviposition or egg laying. [8] The decrease of the gonotrophic cycles implies an increase of the biting frequency from an average of once every five days to once every three days. In turn this could potentially lead to an increase in malaria transmission when infected humans are available.

Deforestation for the purpose of logging and self-subsistence agriculture is a serious problem in the tropical regions of Africa. For Example, Malava forest, a tropical rainforest in kakamega district, Kenya, shrank from 150km2 in 1965 to 86km2 in 1997.In East African highlands, 2.9 million hectares of forest were cleared between 1981 and 1990, representing an 8% reduction in forest cover in one decade. [9] Land use and land cover changes may modify the temperature and relative humidity of malaria vector habitats in the highlands. For instance, deforestation in Cameroon caused the introduction of A. gambiae into the habitat that was previously dominated by A. moucheti.[10]


Deforestation of Mangroves

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A red mangrove, Rhizophora mangle

Mangroves are the salt-tolerant evergreen forests, found in the intertidal zones of sheltered shores, estuaries, tidal creeks, backwaters, lagoons, marches and mudflats of the tropical and subtropical latitudes. Mangrove systems are in continuous jeopardy. Facing threats due to reckless and ruthless human interventions. This constant interference in mangrove forests has made the system to shrink in an alarming way at a faster rate than inland tropical forests and coral reefs.[11] It is predicted that relatice sea level rise can be the greatest threat to the existing mangroves [12] the mangrove forest are likely to be totally lost in the next 100 years, if the present situation continues further.[11] A healthy mangrove ecosystem provides vast benefits to the adjoining systems and mankind. Mangroves and associated soils can sequester 22.8 million metric tons of carbon each year, that is 11% of the total input of terrestrial carbon into the ocean [13] and provides more than 10% of essential organic carbon to the global oceans [14]Carbon sequestration potential of mangroves is 50 times greater than many other tropical forests. This is due to the high levels of below ground biomass and also the considerable storage of organic carbon in mangrove sediment soils. Failing to preserve mangrove forests may cause considerable carbon emiisions and thus accelerate the global warming. [15] The restoration of mangroves can be a ideal and natural counter-measure for global warming. Mangroves also play a key role in environmental security. This consists of mitigating the effects of tsunami, cyclones, floods and green house gas. In general, every ecosystem provides life supporting functions as well as other valuable services, many of which are interlaced with human welfare [16] Mangroves have a medicinal value aswell. Coastal ecosystems such as mangroves are as a potential site for new drugs. [17] Drug research groups have pointed out that mangroves possess an untapped source of new medicines and in the future this ecosystem will be the new frontiers for drug discoveries. [17]

  1. ^ a b c Afrane, Yaw A.; Githeko, Andrew K.; Yan, Guiyun (2012). "The ecology of Anopheles mosquitoes under climate change: case studies from the effects of deforestation in East African highlands". Annals of the New York Academy of Sciences. 1249: 204–210. doi:10.1111/j.1749-6632.2011.06432.x. PMC 3767301. PMID 22320421. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: date and year (link)
  2. ^ IPCC (2007). Climate Change 2007: Impacts, Adaptation, and Vulnerability. Cambridge: Cambridge University Press.
  3. ^ Lindsay, S.W. & Birley, M.H. (1996). "Climate change and malaria transmission". Ann. Trop. Med. Parasitol. 90 (6): 573–588. doi:10.1080/00034983.1996.11813087. PMID 9039269.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ Afrane, Y.A., Zhou, G., Lawson B.W. (October 2007). "Life-table analysis of Anopheles arabiensis in western Kenya highlands: Effects of land covers on larval and adult survivorship". The American Journal of Tropical Medicine and Hygiene. 7 (4): 660–666. doi:10.4269/ajtmh.2007.77.660. PMID 17978067.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  5. ^ Gillooly, J.F., Brown, J.H., West, G.B.,Savage, V.M.,Charnov, E.L. (September 2001). "Effects of Size and Temperature on Metabolic Rate". Science Magazine. 293 (5538): 2248–2251. doi:10.1126/science.1061967. PMID 11567137.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  6. ^ Munga, S., Minakawa, N., Zhou, G., Githenko, A.K., Yan, G. (September 2007). "Survivorship of Immature Stages of Anopheles gambiae s.l. (Diptera: Culicidae) in Natural Habitats in Western Kenya Highlands". Journal of Medical Entomology. 44 (5): 758–764. doi:10.1603/0022-2585(2007)44[758:SOISOA]2.0.CO;2. PMID 17915505.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  7. ^ Afrance, Y.A., Lawson, B.W., Githeko, A.K., Yan. G. (2005). "Effects of microclimatic changes caused by land use and land cover on duration of gonotrophic cycles of Anopheles gambiae (Diptera: Culicidae) in western Kenya highlands". Journal of Medical Entomology. 42 (6): 974–980. doi:10.1603/0022-2585(2005)042[0974:EOMCCB]2.0.CO;2.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Santos, R.L., Forattini, O.P., Burattini, M.N. (November 2002). "Laboratory and field observations on duration of gonotrophic cycle of Anopheles albitarsis s.l. (Diptera: Culicidae) in southeastern Brazil". Journal of Medical Entomology. 39 (6): 926–930. doi:10.1603/0022-2585-39.6.926. PMID 12495194.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  9. ^ Lindblade, K.A., Walker, E.D., Onapa, A.W.,Katungu, J., Wilson, M.L. (April 2000). "Land use change alters malaria transmission parameters by modifying temperature in a highland area of Uganda". Tropical Medicine & International Health. 5 (4): 263–274. doi:10.1046/j.1365-3156.2000.00551.x. PMID 10810021.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  10. ^ Manga, L., Toto, J.C., Carnevale, P. (March 1995). "Malaria vectors and transmission in an area deforested for a new international airport in southern Cameroon". Societes Belges Medicine Tropicale. 75 (1): 43–49. PMID 7794062.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  11. ^ a b Duke, N. C.; Meynecke, J.-O.; Dittmann, S.; Ellison, A. M.; Anger, K.; Berger, U.; Cannicci, S.; Diele, K.; Ewel, K. C.; Field, C. D.; Koedam, N.; Lee, S. Y.; Marchand, C.; Nordhaus, I.; Dahdouh-Guebas, F. (2007). "A World Without Mangroves?". Science. 317 (5834): 41–42. doi:10.1126/science.317.5834.41b. PMID 17615322. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: date and year (link)
  12. ^ Gilman, E., Ellison, J., Duke, N.C.,Field, C. (2008). "Threats to mangroves from climate change and adaptation options". Aquatic Botany. 89 (2): 237–250. doi:10.1016/j.aquabot.2007.12.009.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ Jennerrjahn, T.C., Ittekot, V. (January 2002). "Relevance of mangroves for the production and deposition of organic matter along tropical continental margins". Naturwissenschaften. 89 (1): 23–30. doi:10.1007/s00114-001-0283-x. PMID 12008969.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  14. ^ Dittmar, T., Hertkorn, N., Kattner, G., Lara, R.J. (2006). "Mangroves, a major source of dissolved organic carbon to the oceans". Global Biogeochemical Cycles. 20: 7. doi:10.1029/2005GB002570.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ^ Spalding, M., Kainuma, M., Collins, M. (2010). World atlas of mangroves (PDF). p. 319.{{cite book}}: CS1 maint: multiple names: authors list (link)
  16. ^ Farley, J., Batker, D., Del la Torre, I., Hudspeth, T. (September 2009). "Conserving Mangrove Ecosystems in the Philippines: Transcending Disciplinary and Institutional Borders". Environmental Management. 45 (1): 39–51. doi:10.1007/s00267-009-9379-4. PMID 19830480.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  17. ^ a b Regunathan, C., Kitto, M.R. (2009). "Drugs from the indian seas-- More Expectations". Current Science. 97: 1705–1706.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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