The Loss of Butterflies in the UK - Case Study Example

Biodiversity and Agriculture: The Loss of Butterflies in the UK In 2007, the Centre for Ecology and Hydrology, together with the Butterfly Organization, released the latest report on the "The State of Britains Butterflies 2007" (Fox, Warren, Asher, Brereton, & Roy, 2007). Based on millions of butterfly records that were collected through the initiative of the Butterflies for the New Millennium (Butterfly Conservation, 2009) and the UK Butterfly Monitoring Scheme (The UK Butterfly Monitoring Scheme (UKBMS), 2006), the major highlight of the report was the continuing decline of butterflies populations and species of Britain. According to the report, out of the fifty-nine resident species of Britain, 75% are declining while five species are extinct already. Of these, 21 species have reduced populations of more than 30% in the last 25 years while fifteen species have expanded their range, most probably due to changes in climate. Since British butterflies are highly monitored, the changes in their population levels and distribution are important inputs for the UK Biodiversity Action Plan, which formulates actions and policy towards conservation of butterflies and other species (Butterfly Conservation, 2009). On a wider scale, the implications of the findings of the report are significant because butterflies are known to be highly sensitive indicators of environmental changes, not only those brought about by climate, but also due to decreases in the biodiversity of their ranges. Compared to other organisms such as birds, butterflies are easily more affected by changes in biodiversity because they utilize resources on a much finer scale. Therefore, they are more responsive to even small changes in biodiversity. Biodiversity is the totality of all forms of life, comprising the total gene pool of the world. Loss in biodiversity is due to natural and human activities. Increasing human populations result in higher demand for agricultural and industrial products, and energy costs. To supply these demands, agricultural production becomes more intensive and requires high inputs of harmful chemicals and disturbance of large tracts of land. Industry booms, what with the increased requirements for basic needs and other luxuries. All these result in exploitation of the world’s natural and non-renewable resources, and threats to the biodiversity of plant, animal and microbial resources. Conversion of natural habitats to intensive land use, use of new land management practices, and the far-reaching effects of pollution and climate change pose the biggest threats to biodiversity (Chapin III, et al., 2000). The major cause of butterfly declines is the loss of habitat (Fox, Warren, Asher, Brereton, & Roy, 2007). According to Dr. Warren of Butterfly Conservation, extinction of butterfly species result from habitat loss brought about by urban sprawl, poor woodland management or intensive agricultural practices (BBC News, 2006). Other causes of specific butterfly declines are post-industrial destruction of habitats by landscaping or redevelopment and drainage of bogs, which are blamed for the loss of the Dingy Skipper and Large-Heath colonies. Declines of Large Blue and Marsh Fritillary, and Adonis Blue were attributed to reduced grazing, scrub invasion and changes in the natural vegetation (Fox, Warren, Asher, Brereton, & Roy, 2007). Habitats have particular features that are necessary for the completion of life cycle of the resident butterfly species. The habitat should have food for each developmental stage of the butterfly, as well as shelter. Most British butterflies have grassland habitats, thus the proper management of grasslands is important. It has been shown that for a grassland community of butterflies, it was the grassland type that primarily determined the richness and composition of the species. Butterfly diversity can therefore be protected by maintaining high quality grasslands (Collinge, Prudic, & Oliver, 2003). Butterfly species can be categorized to their preference for habitats: ‘specialists’ are those having relatively localized and isolated patches of habitats. Since the distribution of specialist butterflies is limited, they are more affected by habitat loss (Fox, et al., 2001). ‘Generalists’ are mobile species, are more extensively distributed, have wider ranges with habitats and food that are available in the landscape. Compared to the specialists, the generalists show less declines from (Table 1). Nevertheless, the general decline in specialists and generalists indicate that there is a major loss in habitat due to changes in land use and management practices. Agricultural intensification has led to the fragmentation of habitats (Wallis De Vries, Parkinson, Dulphy, Sayer, & Diana, 2007). Habitat specialists, due to their narrow range, are the more affected compared to the generalists (Fox, et al., 2001). If the process of fragmentation of habitats continues then the extinction of species could increase. This was the case for the Large Blue (Maculinea arion) which became extinct in 1979 (Centre for Ecology and Hydrology, 2009). The Large Blue larvae are highly specialized, and adapt only to a single host; an ant species that inhabited a narrow niche in grassland. Due to changes in vegetation structure, the ants disappeared, resulting in the extinction of the Table 1. Trends in butterfly indicators in England (Eng), Scotland and the UK from 1976 to 2006. (Figure from Botham, Brereton, Middlebrook, Cruickshanks, & Roy, 2008) Large Blue. Identification of this event has resulted in a recovery and conservation effort that spanned twenty-five years and resulted in the return to UK of the Large Blue butterfly (Thomas, Simcox, & Clarke, 2009). Reversion of the declines can be achieved through the improvement and rehabilitation of habitats by implementing the proper maintenance of grassland maintenance, better woodland management and use of agri-environment schemes (Botham, Brereton, Middlebrook, Cruickshanks, & Roy, 2008). The problem of the decline in butterfly species and habitat loss has been recognized decades ago. At the forefront of butterfly conservation efforts is the organization aptly named Butterfly Conservation, formed in 1968 by a group of naturalists. Then known as the British Butterfly Society, its aim was to stop the alarming decline of Britain’s Lepidoptera species (moths and butterflies), and to simultaneously work towards environmental protection and conservation (Butterfly Conservation, 2009). Now the largest insect conservation group in Europe, it is involved in funding, coordination, research, and policy. Butterfly Conservation has been at the forefront of the monitoring and record maintenance for sightings of butterflies and moths. It is also involved in landscape-scale conservation of butterflies, maintenance of nature reserves, research on habitat requirements, and the assessment of the impacts of climate change and policies. Aside from Butterfly Conservation, other groups are also involved in research on factors affecting biodiversity and butterfly loss. These are government research institutions, private and public universities, and other conservation groups. Studies have been conducted to assess the effects of different agricultural activities on habitat biodiversity with the objective of limiting the decline in butterfly species and at the same time maintaining agricultural productivity. The determination of species decline starts with knowing the baseline number of the different species in their different habitats. This is achieved by monitoring butterfly populations in the different localities in the UK. This effort is coordinated by the Butterfly Conservation and the UK Butterfly Monitoring Scheme [The UK Butterfly Monitoring Scheme (UKBMS), 2006]. The “Butterflies for the New Millennium” (BNM) is Butterfly Conservations general recording scheme for surveying all species of butterfly. BNM is largely served by volunteers and is a cooperative effort with other agencies in the UK. Butterfly populations are mainly determined by recording butterfly sightings. A method has been developed for recording butterfly sightings, and all volunteers involved in the BNM are provided with the methodology. Called the transect method, it involves the establishment of a fixed-route walk (transect). An ideal transect is 2-4 km long, to be walked from 45 minutes to 2 hours. Butterfly sightings are recorded during a weekly walk along the route (The UK Butterfly Monitoring Scheme (UKBMS), 2006). The transect route is fixed to enable yearly comparison of sightings. The butterfly sightings are only recorded if they occur in a fixed width along the transect, from April to September, and only between 10.45in the morning to 3.45pm on days that allow for butterfly activity. In recent years, single species transects have been established. These transects follow the standard protocol, but normally less time is required to walk single species transects. Single species transects have allowed for monitoring populations of threatened butterfly species. All the data are subjected to statistical analysis to calculate the index of abundance for the butterfly species [The UK Butterfly Monitoring Scheme (UKBMS), 2006]. Habitats and the biodiversity within the habitat are characterized by sampling plots or quadrants for different plant, animal and insect species. Habitat quality is assessed by preferences of the ovipositing female or the presence of larvae (Thomas, et al., 2001). Preference is measured by determining the number and species of food-plants in different developmental stages that specific butterfly larva are known to feed on. Using the transect method, data since 1976 show that the population of specialist habitat butterflies has an apparent decline of 70 % while the generalist populations declined by 45 % (Trends in populations of selected species (butterflies), 2009) (Figure 1). The large fluctuations in the values between years are typical of butterfly populations; therefore, Butterfly Conservation analyzed the underlying trends. The trend analysis verified the significant decline in specialist’s population, but there is no overall change in the generalists. Habitat specialist species, which are easily affected by loss and fragmentation of their natural habitats have not recovered from population losses brought about by the drought in 1976 (Botham, Brereton, Middlebrook, Cruickshanks, & Roy, 2008). Figure 1. Changes in populations of butterfly species from 1976-2006. Loss in biodiversity has been attributed to increased intensive and monoculture farming. Efforts to counter the loss have centred on promoting organic farming. Previous studies, which compared the effect of organic and conventional farming on butterfly populations, have conflicting results. Organic farms have recorded higher abundance of butterflies in crop edges and field boundaries, resulting from the higher prevalence of non-pests butterflies (Feber, Firbank, Johnson, & McDonald, 1997). Interestingly, these butterflies were found on the field margins rather than on the crop itself. Increased abundance in food-plants in the field boundaries was cited to be responsible for the higher number of pests on the crop edges. In another study, it was shown that there were no significant effects of both organic and conventional farms on butterfly population, on species richness and abundance. (Weibull, Bengsston, & Nohlgren, 2000). A more recent study compared the effect of organic farming and conventional farming using a landscape-scale experiment to determine differences on increasing butterfly species abundance (Rundlöf, Bengtsson, & Smith, 2008). Locally, organic farming increased the richness and abundance of butterfly species. The interaction of local and landscape farming within fields had a more significant effect on abundance if the area was surrounded by conventional farms instead than organic farms. This meant that butterflies favoured the organic farm. Higher within field diversity contributed to the total abundance of observed butterfly species. The loss of butterflies is a direct and clear indicator of loss of biodiversity. For humankind, the loss in biodiversity is equivalent to losing humanity’s heritage, which has been developed for over millions of years. The number of habitats destroyed, fragmented, and endangered by anthropogenic activities is continually increasing, resulting in disturbed ecosystems and loss of vital genetic resources. The practice of agriculture is one of the major causes of the loss in biodiversity, resulting in a dearth of genetic resources for the improvement of crop and animal species. Monoculture will eventually lead to lower productivity, based on the results of biodiversity experiments that show that more plant species within a field lead to greater productivity in a plant community (Tilman, 2000). The links to ecosystems of biodiversity have intellectual, cultural, and spiritual values that are important to society (Chapin III, et al., 2000). More importantly, altered functions of the ecosystem are important economically because of the effects on the delivery of goods and services to meet society needs. Loss in biodiversity can lead to adverse effects on ecosystems that can reduce food, structural, medicinal, and genetic resources. The increased maintenance costs due to invasion of predatory plant species on plant ecosystems can sufficiently increase costs of basic services or even compete for the use of scarce resources. This has been the case when deep-rooted species in arid regions compete with humans for the water resources. Loss of endemic species and their replacement with new invasive species can disturb the ecosystems on a large economic scale. An example would be the fires in Western United States that were due to cheatgrass proliferation. Factors that result in losses and changes in biodiversity can be regulated by changing policies on land use, greenhouse gas emissions, and species introductions (Chapin III, et al., 2000). It is proposed that the scientific community should strengthen its efforts to identify threshold responses of the ecosystems to changes in biodiversity. The public, policy-makers, and other stakeholders should be informed and made aware of the irreversibility of these alterations. Although scientific evidence points to the societal impact of changing biodiversity, the public is not aware that the changes are permanent and not reversible. Land use managers must consider the ecological and social effects of biodiversity change. Managed landscapes are recommended to control loss in biodiversity. In all instances, political will must be exercised, and citizens should collaborate with local to national levels of government in the implementation of regulations and policies geared towards the reduction of environmental damage and changes in biodiversity. The efforts towards increasing butterfly population, such as landscape-scale conservation experiments and use of nature reserves, must be duplicated in more areas at a much larger scale. Butterfly conservation is also biodiversity conservation. Understanding our world, our habitat, should be approached in the manner that was employed to understand the habitat of the previously extinct Large Blue butterfly. Restoring our habitat means also restoring the biodiversity that shelters, protects, and sustains us. Works Cited (2009). Retrieved December 9, 2009, from Butterfly Conservation: http://www.butterfly-conservation.org/text/6/conservation.html BBC News. (2006, July 22). UK butterfly species down to 56 . BBC News, available online from http://news.bbc.co.uk/2/hi/science/nature/5205358.stm. Botham, M., Brereton, T., Middlebrook, I., Cruickshanks, K., & Roy, D. (2008). United Kingdom Butterfly Monitoring Scheme report for 2007. Wallingford: Center for Ecology and Hydrology. Centre for Ecology and Hydrology. (2009, 16 June). Large blue butterfly: on a wing and a prayer. CEH Web. Chapin III, F., Zavaleta, E., Eviner, V., Naylor, R., Vitousek, P., Reyolds, H., et al. (2000). Consequences of changing biodiversity. Nature, 405, 234-232. Collinge, S., Prudic, K., & Oliver, J. (2003). Effect of local habitat characteristics and landscape context on grassland butterfly biodiversity. Conservation Biology, 17 (1), 178-187. Feber, R., Firbank, L., Johnson, P., & McDonald, D. (1997). The effects of organic farming on pest and non-pest butterfly abundance. Agriculture, Ecosystems and Environment, 64, 133-139. Fox, R., Warren, M., Asher, J., Brereton, T., & Roy, D. (2007). The state of Britain’s butterflies 2007. Wareham, Dorset: Butterfly Conservation and the Centre for Ecology and Hydrology. Fox, R., Warren, M., Harding, P., McLean, I., Asher, J., Roy, D., et al. (2001). The state of Britains butterflies. Wareham: CEH and JNCC. Methods for recording butterfly transects. (2006). Retrieved December 9, 2009, from UK Butterfly Monitoring Scheme: http://www.ukbms.org/methods.htm Rundlöf, M., Bengtsson, J., & Smith, H. (2008). Local and landscape effects of organic farming on butterfly species richness and abundance. Journal of Applied Ecology, 45 (3), 813-820. The UK Butterfly Monitoring Scheme (UKBMS). (2006). Retrieved December 9, 2009, from The UK Butterfly Monitoring Scheme: http://www.ukbms.org/ Thomas, J., Bourn, N., Clarke, R., Stewart, K., Simcox, D., Pearman, G., et al. (2001). The quality and isolation of habitat patches both determine where butterflies persist in fragmented landscapes. Proceedings of the Royal Society in London B , 268, 1791-1796. Thomas, J., Simcox, D., & Clarke, R. (2009). Successful conservation of a threatened Maculinea butterfly. Science [online], DOI: 10.1126/science.1175726. Tilman, D. (2000). Causes, consequences and ethics of biodiversity. Nature, 405, 208-211. Trends in populations of selected species (butterflies). (2009, March). Retrieved December 10, 2009, from Joint Nature Conservation Comittee: http://www.jncc.gov.uk/page-4236 Wallis De Vries, M., Parkinson, A., Dulphy, J., Sayer, M., & Diana, E. (2007). Effects of livestock breed and grazing intensity on biodiversity and production in grazing systems. 4. Effects on animal diversity. Grass & Forage Science, 62 (2), 185-197. Weibull, A-C., Bengsston, J., & Nohlgren, E. (2000). Diversity of butterflies in the agricultural landscape: the role of farming system and landscape heterogeneity. Ecography, 23, 743-750. Read More