毕业论文英文 Impacts Of Biofuel Expansion In Biodiversity Hotspots
The finitude of fossil fuels, concerns for energy security and the need to respond to climate change have led to growing worldwide interests in biofuels. However, a significant proportion of conventional biofuel feedstocks is produced in biodiversity hotspots in the tropics, notably oil palm in Southeast Asia, and soy and sugarcane in Brazil. This is a worrying trend for many tropical biologists because it is also within the tropics where majority of the worldï¿½s biodiversity hotspots are located (Myers et al. 2000). For at least the next decade, first generation biofuels will still be in demand. In biodiversity hotspots, where a myriad of anthropogenic factors are already driving intense land use conflicts, biofuels production will pose an additional challenge to the preservation of the remaining natural habitats. Here we address the following questions: How does biofuel expansion threaten biodiversity hotspots? How can we reconcile biofuel expansion with biodiversity conservation in these hotspots?
X.1. Biofuels in biodiversity hotspots
Approximately 80% of total world energy supply is derived from fossil fuels such as oil, natural gas and coal. Fossil fuels are finite sources of energy and are estimated to last anywhere from 41 to ~700 years, depending on production and consumption rates (Goldemberg and Johansson 2004; Goldemberg 2007). Growing demand for energy from industrialized nations, such as the U.S., as well as emerging economies, such as China and India, will continue to place tremendous pressures on world petroleum supplies in the next few decades (Worldwatch Institute 2007). This trend is reflected in the price of crude oil, which has risen from ~US$25 per barrel in January 2000 to ~US$76 per barrel in January 2010 (peaking at ~US$140 per barrel in June 2008) (EIA-DOE 2010). As such, many countries are seeking to diversify their energy portfolio. Growing concerns over anthropogenic climate change have also driven countries to search for alternatives to fossil fuels that can help lower greenhouse gas emissions and slow the pace of global warming.
These pressing global energy and environmental challenges have at least partly driven the recent worldwide interest in biofuels. Both developed (e.g. the U.S.) and developing nations (e.g. China) view biofuels as a renewable energy source that can help achieve energy security, decrease greenhouse gas emissions and fulfill rural development standards (Fulton et al. 2004, Armbruster and Coyle 2006, Pickett et al. 2008). Between 1980 and 2005, global biofuel production increased from 4.4 to 50.1 billion litres (Murray 2005, Armbruster and Coyle 2006). Recently, several of these countries have also announced ambitious targets for switching from fossil fuels to renewable fuels (Worldwatch Institute 2007).
Biofuels are renewable fuels derived from biological feedstocks. Currently, the most widely used liquid biofuels in the transportation sector are bioethanol and biodiesel. Bioethanol is produced from the fermentation of corn (Zea mays), sugar-cane (Saccharum spp.), or other starch- or sugar-rich crops. Biodiesel is manufactured from vegetable oil (e.g. soybean (Glycine max L.), oil palm (Elaeis guineensis) or animal fats. At present, bioethanol is primarily produced from corn in the U.S., and from sugarcane in Brazil. Biodiesel is produced largely from rapeseed and sunflower seed oil in Europe, and soybean oil in the U.S. However, there is a steadily growing demand for palm oil produced in the tropics due to its much higher yield (~5,000 litres per ha compared to ~1,200 litres per ha for rapeseed), and hence lower production costs (Worldwatch Institute 2007). This is a worrying trend for many tropical biologists because it is also within the tropics where majority of the worldï¿½s biodiversity hotspots are located (Conservation International 2010; www.biodiversityhotspots.org). Furthermore, high proportions of yet forested lands in these hotspots may be suitable for biofuel production (Table 1). A recent study estimated that an increase in global biodiesel production capacity to meet future biodiesel demands (an estimated 277 million tons per year by 2050) may lead to potential habitat losses of between 0.4 million to 114.2 million ha within these hotspots, depending on the feedstock (Koh 2007). Without proper mitigation guidelines, the future expansion of biodiesel feedstock production in biodiversity hotspots will likely threaten their native biodiversity (Mittermeier et al. 2004).
Some researchers argue that ï¿½next generationï¿½ biofuels, produced from non-food feedstocks such as agricultural wastes, can fulfill many of the promises of renewable fuels without much of the environmental ills. These second and third generation biofuels are currently too costly to be produced on a commercial scale. Nevertheless, they may become more readily available and affordable in the future through technological breakthroughs, driven by strong governmental support and a string of local government and international subsidies and initiatives (Doornbosch and Steenblik 2007). Even so, next generation biofuels may not be completely free of environmental tradeoffs. A recent study that analyzed the potential environmental impacts of a global, aggressive cellulosic biofuels programme, projected major losses for biodiversity within biodiversity hotspots both directly, by replacing native habitats, or indirectly, by displacing other agricultural land uses onto native habitats (Melillo et al. 2009).
For at least the next decade, first generation biofuels will still be in demand (OECD-FAO 2008). In biodiversity hotspots, where a myriad of anthropogenic factors are already driving intense land use conflicts, adding biofuels as another demand on the land will make the preservation of the remaining natural habitats an even greater challenge. Hence, it is imperative for us to assess the impacts of biofuel expansion on biodiversity hotspots by asking the following two questions: (1) How does biofuel expansion threaten biodiversity within biodiversity hotspots? (2) How might we reconcile biofuel expansion with biodiversity conservation in these hotspots?
X.2. How does biofuel expansion threaten biodiversity within biodiversity hotspots?
X.2.1. Habitat loss