It is important for every ecosystem to maintain a balance between all the food chains so that nature can maintain its balance. Although natural ecosystems are under diverse challenges from anthropogenic activities, the ecological impacts of such processes often are unclear. Some “threats” may be worse than we think, but others may be less harmful. For example, invasive species disrupt the functioning of important components of natural ecosystems in many ways, including predation, competition, and disease transfer. (Rolls 1969).
Indeed, conventional wisdom interprets any change wrought by invasive taxa as negative, in that it alters an existing (“natural”) state. However, some changes wrought by invasive taxa might be seen as ‘‘good’’ in ecological terms, for example if they reduce the impact of a previous invader (e. g. Cactoblastis vs. prickly pear: Freeman 1992) or if the new invader fulfils an important ecological role (e. g. pollination, predation) previously performed by a now-extinct taxon (Flannery 1994; Donlan et al. 2005). Disease transfer agents are an immense threat to human health and pests are the most common disease transfer vectors.
Mosquitoes are one of the most efficient and hazardous transfer vectors that pose a constant threat for human health as they grow rapidly in very unlikely conditions as well. Over recent years, in order to overcome this threat and to find a solution to this problem researchers and scientists have done serious work. If we are able to find out the reasons why and how mosquitoes survive, multiply and spread then we will be able to control their growth and limit the trouble they cause to both humans and wild life.
Although when research on such subjects undergoes, we tend to ignore the positive impacts of the invasive species and focus too much on their negative aspects whereas there can be some positive aspects that can prove beneficial for the society. To interpret the impact of these invasive species, we need to take into account all their aspects and implement studies on the multiplicity of factors. Any overall assessment of the impact of an invasive species needs to consider both the possible benefits (e. g. to human health) as well as negative effects (e. g. to native species).
The situation becomes far more complex if we include evaluations by the public as well as by professional ecologists. Ultimately, the decision that a given impact is ‘‘good’’ or ‘‘bad’’ is a subjective one, reflecting priorities and value systems that diverge widely among different sectors of the population. Therefore, it is important to conduct the experiments and researches to include and project both the aspects and then the influence and use of the invasive species. Here we have tried to include both the aspects of amphibians and their impacts on human health and pests.
Taking into account three research articles, cited in bibliography, we would try to understand the relation between amphibians, pests and human health. One of the natural factors that regulate the population of pests is predation by amphibians mostly. In these researches, we find that they have compared different species of amphibians and their role in controlling the growth and population size of mosquitoes specifically, as they have devised that mosquitoes are the major transfer vectors of diseases in humans. Sarah E. Durant and William A.
Hopkins determined in their research the mosquito consumption of two amphibian species, adult red-spotted Newts (Notophthalmus viridescens (Rafinesque 1820)) and larval mole salamanders (Ambystoma talpoiduem (Holbrook 1838)). They also compared the mosquito consumption of eastern mosquito fish (Gambusia halbrooki (Girard 1859)) a known predator of mosquitoes and A. Talpoideum. Both salamander species were capable of consuming large no. of mosquito larvae every day. In A. Talpoideum mosquito consumption scaled with body size, with largest individual (4. 4g) intakes 902 mosquitoes in 1 day.
Gambusia halbrooki consumed 3. 5 times more mosquitoes during a 24 hrs feeding trial than similar-sized A. Talpoideum. Their findings suggested that amphibians could have a substantial impact on control of mosquitoes especially because amphibians can reach densities of up to 500 000 individuals/ha. They further hypothesized that introduction of G. halbrooki could reduce abundances of native mosquito predators (e. g. salamanders) indirectly through competition of invertebrate pray. Michael J et al also conducted research and published a paper on the subject hat how wetlands play a part in aiding controlling of population size and growth rate of mosquitoes. Wetlands are of great advantage to human societies but they are also a threat as they are a major source of mosquito production and growth and thus pose a threat to human health. As increase in mosquito population is a threat to human health, it is important to find out how to counter this threat. They found that in the northeastern US, larval spotted salamanders (Ambystoma maculatum) and wood frog tadpoles (Lithobates sylvaticus) are common in pools and may affect mosquito growth and survival through predation or competition.
To determine if these species interact, they conducted surveys of pools and found that larval mosquitoes were less abundant in pools with higher densities of larval salamanders. Experiments on mosquito oviposition and survival found that mosquitoes avoided ovipositing in habitats containing larval salamanders and tadpoles and had low survival in the presence of salamanders. These data indicate that predation by larval salamanders may influence the breeding distribution of mosquitoes by imposing selective pressure on ovipositing adults.
Mattias Hagman and Richard Shine also conducted research on similar theme. They came across the knowledge that spread of the South American cane toad (Bufo marinus) through tropical Australia is widely viewed as an ecological catastrophe, but anecdotal reports suggest that the invasion of toads may reduce the numbers of mosquitoes (and thus, potentially, the risk they pose to human health). They experimented to determine whether the presence of toad tadpoles affects survival rates, adult body sizes and/or rates of oviposition of four species of disease-carrying mosquitoes.
In the laboratory, the presence of toad tadpoles significantly reduced the sizes of adult mosquitoes at emergence, and reduced survival rates of the larvae of one mosquito species. In field trials, mosquitoes were less likely to oviposit in water bodies containing toad tadpoles. This signifies that presence of amphibians affects the growth of mosquitoes. Aforementioned works determine that somehow amphibians do play a vital role in human health and pest control through predation and competition. This proves they have a great impact in balancing the ecosystems.
Mosquitoes are the most vital transfer vectors and disease carriers thus a threat to human health. With this, increasing threat and widely spread human diseases caused one way or the other by mosquitoes, we can say amphibians are the most natural and harmless (if controlled) counter measures to control the growth and population of mosquitoes. All these works conclude, as it is apparent that amphibians can control mosquitoes then we should try to save the amphibians and take measures to ensure increase in their growth and population size.
The problem is that there is an immense decrease in amphibian population and amphibians can control mosquitoes then to make sure that amphibians grow in population size serious efforts are required. The significance of this effect for mosquito populations will depend upon many as-yet unstudied factors such as the attributes of alternative water bodies, the proportion of potentially suitable water bodies occupied by tadpoles, and the temporal overlap in breeding seasonality of toads and mosquitoes. The second major issue addressed by their results is that of value judgements about “good” or “bad” effects of invasive species.
Despite the benefits of amphibians in controlling mosquitoes, it is vital to maintain a balanced amphibian growth or this itself will create a big problem. As the juvenile and adult stages of the amphibians that breed in seasonal pools over winter and forage in the terrestrial habitat surrounding pools (Calhoun et al. 2005; Rittenhouse and Semlitsch 2007), protecting the upland habitat surrounding pools is necessary to protecting viable breeding populations of amphibians (Gibbons 2003; Harper et al. 008). Protecting the terrestrial habitat surrounding pools involves the conservation of large areas of land that requires obtaining public support for the development of appropriate conservation measures (Calhoun and Reilly 2008). By demonstrating that if, the balanced growth of amphibian population controls mosquito population size and highlight the positive effects of the controlled balance in the ecosystem; this practice can become systemized leading to better human health.
Daszak, P. , Cunningham, A. A. , Hyatt, A. D. 2003. Infection disease and amphibian population declines. Diversity and Distribution. 9:141-150 Hopkins,W. 2012. Wildlife Ecotoxicology and Physiological Ecology Program. The Virgin Tech Press. Blackburg. Rubbo, M. , Lanterman, J. L. , Falco, R. C. , and Daniels, T. J. 2011. The influence of amphibian on mosquitoes in seasonal pools: can wetlands protection help to minimize disease risk? Wetland. 31:7999-804 Gibbons, J. W. Winne, C. T. , Scott, D. E. , Willson, J. D. , Glaudas, X. , Andrew, K. M. , Todd, B. D. , Fredewas, L. K. , Wilkinson, L. , Tasalliagos, R. N. , Harper, S. J. , Greene, J. L. , Tuberville, T. D. , Metts, B. S, and Dorcas, M. E. 2006. Remarkable amphibiban biomass and abundant isolated wetland: Implications for wetland conversation. Conversation of biology. 20:1457-1465 Shine,R. 2006. The ecological impact of invasive cane toad( Bufo marinus) in Australia. University of Sydney Press.