毕业论文英文 Impacts Of Biofuel Expansion In Biodiversity Hotspots
Currently, biodiversity hotspots in Southeast Asia and Latin America are under the greatest threat of biofuel expansion, namely from oil palm, sugarcane and soybean expansion. Based on land-cover data compiled by the Food and Agricultural Organisation of the United Nations, Koh and Wilcove (2008) calculated an expansion of 1.8 million ha of oil palm in Malaysia and 3 million ha in Indonesia between 1995 and 2005. Approximately 55-59% of this oil palm expansion in Malaysia and at least 56% of that in Indonesia occurred at the expense of primary or logged over forests. In Brazil, the area of soybean expansion increased dramatically by 10 million ha, from 11.6 million to 22.9 million ha between 1995 and 2005 (FAO 2010). Successful expansion of soybean has been driven by a biotechnological breakthroughï¿½the development of soybean-bacteria combinations with pseudosymbiotic relationships, which allows soybeans to be planted with little or no application of nitrogen fertilizers (Fearnside 2001)). Although much of this soybean expansion has occurred on non-forested lands, particularly in the Cerrado, this natural grassland ecosystem nonetheless contains high concentrations of endemic and threatened species and has been delineated as a biodiversity hotspot (Fearnside 2001). Sugarcane expansion in Brazil has almost doubled from 4.5 million ha in 1995 to 8.1 million ha in 2008, with a rapid increase of 2.3 million ha between 2005 and 2008 (FAO 2010). Even though sugarcane plantings so far have mostly replaced pasture lands, continued expansion of sugarcane-bioethanol into the Center West of Brazil will likely displace cattle ranchers and soybean producers onto the Amazon and Atlantic Forest and lead to extensive deforestation (Martinelli and Filoso 2008; Lapola et al. 2010). The expansion of biofuel industries is not the only cause of habitat loss in these areas; other causes include large-scale commercial logging, pulp and paper industries, cattle ranching, shifting cultivation, mining, urban development and agricultural expansion of other crops (Angelsen and Kaimowitz 1999). However, growing global demand for palm oil, soybean and sugarcane for biofuels will likely exacerbate deforestation in these hotspots over the next decade (IATP 2008).
X.2.2. Biodiversity loss
Conversion of natural habitats into monocultures, by definition, implies a drastic loss in biodiversity and change in the composition of species communities in the area. Oil palm plantations contain less than half as many vertebrate species as primary forests (Fitzherbert et al. 2008). Forest bird species declined by 73%-77% (Koh and Wilcove 2008) and only 10% of mammal species were detected in oil palm plantations (Maddox et al. 2007). Endangered species such as the Sumatran tiger (Panthera tigris sumatrae), tapirs (Tapirus indicus) and clouded leopards (Neofelis nebulosa) were never recorded in oil palm plantations; and most mammals even preferred marginal and heavily degraded landscapes, such as shrublands, to oil palm (Maddox et al. 2007). Mammals that do occur in oil palm plantations tend to be of low conservation value, and are dominated by a few generalist species such as the wild pig (Sus scrofa), bearded pig (Sus barbatus), leopard cat (Prionailurus bengalensis) and common palm civet (Paradoxurus hermaphroditus) (Maddox et al. 2007). On the other hand invertebrate taxa showed greater variation between oil palm plantations and natural forests (Fitzerherbert et al. 2008). For example, the conversion of forests to oil palm caused forest butterfly species to decline by 79%-83% (Koh and Wilcove 2008); whereas ants, moths and bees showed a higher total species richness in oil palm than forests (Danielsen et al. 2009). Nevertheless, studies consistently showed a dominance of non-forest invertebrate species in oil palm plantations (Danielsen et al. 2009). Comparing across both vertebrate and invertebrate taxa, a mean of only 15% of species recorded in primary forest could be found in oil palm plantations (Fitzherbert et al. 2008). Not surprisingly, plant diversity within oil palm plantations was impoverished compared to forests due to regular maintenance and replanting (every 25 to 30 years) of oil palm fields (Fitzherbert et al. 2008; Danielsen et al. 2009). Biodiversity loss from soybean and sugarcane production has not been as well studied as oil palm but is expected to be significant by virtue of large scale natural habitat conversion (Fearnside 2001). The Cerrado is the largest savanna region in South America and contains a rich diversity of different vegetation types, from tree and scrub savanna, grasslands with scattered trees and patches of dry, closed canopy forests known as the Cerradï¿½o (Conservation International 2010). This region contains a large number of plant (10,000 species) and animal species (2,000 species), including many endemic species such as the maned wolf (Chrysocyon brachyurus), the giant armadillo (Priodontes maximus) and the giant anteater (Myrmecophaga tridactyla) (Conservation International 2010). The ecotone between forest and cerrado is also rich in endemic plant species (Fearnside and Ferraz 1995). Unfortunately, this ecosystem has also been widely cleared for soybean expansion as it is the least protected ecosystem in Brazil, with only 1.5% protected within federal reserves (Casson 2003).
X.2.3. Environmental pollution
Apart from habitat loss, biofuel industries can threaten biodiversity hotspots by causing environmental pollution and degradation through poor farming practices. Inappropriate management practices such as intensive usage of fertilizers and pesticides as well as using fires for land clearing could lead to environmental problems such as soil degradation, and water and air pollution, which in turn could lead to long-term ecological impacts on these biodiversity hotspots. For soybean and sugarcane, which are both annual crops, the ecosystem of the agricultural landscape is disrupted yearly and requires high inputs of fertilizers, pesticides and weed control to maintain high levels of production (Casson 2003; Martinelli and Filoso 2008). For sugarcane production, bare soils are exposed to intense winds and rains during management practices which can result in soil erosion rates of up to 30 tons/ha/year (Sparovek and Schnug 2001; Martinelli and Filoso 2008). Soil erosion as a result of soybean cultivation amounts to similar rates of losses between 19 and 30 tons/ha/year depending on soybean management practices, land aspect and soil type (Tomei and Upham 2009). Mature oil palm plantations in Malaysia have a soil erosion rate of approximately 7.7 to 14 tons/ha/year (Hartemink 2006). Soil erosion in oil palm plantations can be even more serious in the early years when a complete palm canopy has not yet been established, which is why maintaining a legume crop cover is important to protect against soil erosion (Corley and Tinker 2003).
Surface runoff as a result of soil erosion brings organic matter and agro-chemicals into aquatic systems which can lead to deterioration of aquatic habitats and affect the biodiversity downstream. For example, contaminants such as atrazine, a herbicide used in sugarcane crops, and heavy metals like copper, were found in water samples and stream bed sediments collected from waterways flowing through areas of extensive sugarcane cultivation (Carvalho et al. 1999, Azevedo et al. 2004, Corbi et al. 2006). High levels of nitrogen fertilizer used for sugarcane crops can lead to the excessive accumulation of nitrogen into aquatic systems. Filoso et al. (2003) reported high rates of nitrogen export into rivers draining watersheds such as the Piracicaba and Mogi river basins which are heavily cultivated with sugarcane. As a legume, soybean cultivation requires little nitrogen inputs but do require agrochemicals to combat diseases, weeds and pests. The concentration of these agrochemicals in water bodies surrounded by soybean plantations may also accumulate in fishes caught for human consumption (Fearnside 2001). Waste products and by-products of the industrial processing of sugarcane and palm oil into ethanol and crude palm oil respectively are highly pollutive and are a large source of pollution if released into the environment without proper treatment. Palm oil mill effluent (POME) and vinasse from sugarcane distillation are rich in organic matter and contribute to eutrophication and depletion of dissolved oxygen levels in aquatic systems if left untreated (Donald 2004; Martinelli and Filoso 2008). Despite the existence of present technologies to treat mill effluents, it is not uncommon for leakages and discharge from small mills to happen, leading to adverse impacts on aquatic ecosystems (Martinelli and Filoso 2008; Sheil et al. 2009)).
Burning is a common crop management practice in Brazil for facilitating the harvesting of sugarcane and has been used to clear natural vegetation for oil palm and soybean expansion in Indonesia and Brazil (Casson 2003; Martinelli and Filoso 2008; Sheil et al. 2009). The burning of the straw and leaves of sugarcane greatly facilitates the process of harvesting and drives out snakes which may pose a danger to the cane cutters (Martinelli and Filoso 2008). However, it also contributes to a higher concentration of suspended aerosols in the atmosphere (Lara et al. 2005) and leads to increases in soil temperature, decreases in soil water content and soil degradation (Dourado-Net et al. 1999; Oliveira et al. 2000; Tominaga et al. 2002). Oil palm expansion has been partially responsible for the devastating 1997-1998 forest fires in Indonesia, where satellite imagery showed fires were started by oil palm companies to clear land (Dennis et al. 2005). The dry conditions brought about by the El Nino phenomenon exacerbated the fires which burnt 11.6 million ha of land, more than half of which were montane, lowland and peat forests (Tacconi 2003). Fires are used to clear forests because they are a quick and cheap way to clear land (Guyon and Simorangkir 2002) and they lead to forest degradation which allows oil palm companies to acquire land use permits more easily(Casson 2000). In Brazil, the El Nino effect also led to serious droughts in the North and North-East and fires ignited in the savanna areas for pasture and agricultural crops like soybean blazed out of control, contributing to serious forest fires in the North (Casson 2003).
X.2.4. Interaction with other frontier opening activities
The development of biofuel plantations is associated with other drivers of habitat loss and degradation such as industrial activities like logging or cattle ranching and the building of infrastructure such as roads and waterways. This increases the accessibility of natural resources for further exploitation and heightens the level of fragmentation and isolation of remnant natural habitats. Oil palm plantations have been associated with logging companies as the profits obtained from the sale of timber can help cover part of the establishment costs of an oil palm plantation (Casson 2000). In cases where companies seek short-term profits or are unwilling to take the risks in developing oil palm industries in infrastructure-poor regions (e.g. Papua and Kalimantan), application for licenses to establish oil palm estates provide a loophole for these companies to clear-cut forests without the use of sustainable management practices for the timber extracted (Casson 2000). This explains why less than 1 million ha out of 5.3 million ha of land allocated to oil palm development have actually been planted with oil palm in Kalimantan (Casson et al. 2007). The expansion of soybean in Brazil has been linked to both charcoal production and cattle ranching (Casson 2003). Soybean expansion provides access to Cerrado trees which are used by the Brazilian steel industry for charcoal production. Profits generated by selling the Cerrado trees to charcoal producers have helped soybean farmers to further soybean expansion. The degradation of gallery forests due to the extraction of such trees has raised concern as these forests provide a corridor that links the Amazon and the coastal forests with the Cerrado and is an important habitat for several endemic fauna (Tengnï¿½s and Nilsson 2003). The advance of large-scale mechanized soybean farms as a result of government policies and soybean technologies pushed small-scale farmers into the Amazonian frontier where agricultural expansion and pasture development took place at the expense of forests (Skole et al. 1994; Schneider et al. 2000). Fearnside (2001) describes how soybean expansion has led to major infrastructure developments in Brazil and highlights the potential for habitat exploitation due to greater accessibility in the region.
The threats to biodiversity hotspots from biofuel expansion are both direct (habitat replacement and environmental pollution) and indirect (displacement of other activities into natural habitats and increasing accessibility for further exploitation). However, these impacts are not only limited to biofuel production and have surfaced in other agricultural expansion for industry (e.g. rubber [(Li et al. 2007)] and timber (Fredericksen and Putz 2003)]) as well as food production (e.g. rice, coffee, cocoa [see Donald 2004]). The underlying reason for these damaging impacts are poor agricultural practices and policies which focus on the maximization of profits and productivity without taking into consideration the sustainability of the agricultural system and the costs to the environment (IATP 2008). Reducing the biodiversity impacts of biofuel expansion would require a change in production systems and policies and a set of stringent criteria to ensure that biofuels are produced at little cost to biodiversity and ecological systems. Considering the initial environmental reasons for using biofuels over fossil fuels, it would be a cruel irony if they are to be produced at the expense of biodiverse regions and result in more harm than good to the environment.
X.3. How can we reconcile biofuel expansion with biodiversity conservation in these hotspots?
Reconciling biofuel expansion with biodiversity conservation is not a straightforward process due to the links between the biofuel industry and both the agricultural and energy sector. A careful assessment of land use allocation options and major restructuring of the agricultural management system may be required for biofuel expansion to proceed with little or no environmental costs. Additionally, the development of energy-efficient transportation systems and advancement of second and third generation biofuels will help alleviate demand for conventional biofuel feedstocks. However, these actions will require a considerable amount of time, resources and long-term commitment from society. From a biodiversity perspective, there is an added urgency to also work on immediate solutions to minimize the loss of threatened biodiversity to biofuel expansion within these hotspots.