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Accelerating ocean loss causes extinction



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Accelerating ocean loss causes extinction


Alex David Rogers 6/20/11, Ph.D. in marine invertebrate systematics and genetics from the University of Liverpool is a Professor in Conservation Biology at the Department of Zoology, University of Oxford AND Dan Laffoley, PhD on marine ecology at the University of Exeter, and Senior Advisor, Marine Science and Conservation Global Marine and Polar Programme (IPSO Oxford, “International earth system expert workshop on ocean stresses and impacts”, July 20, 2011, http://www.stateoftheocean.org/pdfs/1906_IPSO-LONG.pdf)

The workshop enabled leading experts to take a global view on how all the different effects we are having on the ocean are compromising its ability to support us. This examination of synergistic threats leads to the conclusion that we have underestimated the overall risks and that the whole of marine degradation is greater than the sum of its parts, and that degradation is now happening at a faster rate than predicted. It is clear that the traditional economic and consumer values that formerly served society well, when coupled with current rates of population increase, are not sustainable. The ocean is the largest ecosystem on Earth, supports us and maintains our world in a habitable condition. To maintain the goods and services it has provided to humankind for millennia demands change in how we view, manage, govern and use marine ecosystems. The scale of the stresses on the ocean means that deferring action will increase costs in the future leading to even greater losses of benefits. The key points needed to drive a common sense rethink are: • Human actions have resulted in warming and acidification of the oceans and are now causing increased hypoxia. Studies of the Earth’s past indicate that these are three symptoms that indicate disturbances of the carbon cycle associated with each of the previous five mass extinctions on Earth (e.g. Erwin, 2008; Veron, 2008a,b; Veron et al., 2009; Barnosky et al., 2011). • The speeds of many negative changes to the ocean are near to or are tracking the worstcase scenarios from IPCC and other predictions. Some are as predicted, but many are faster than anticipated, and many are still accelerating. Consequences of current rates of change already matching those predicted under the “worst case scenario” include: the rate of decrease in Arctic Sea Ice (Stroeve et al., 2007; Wang & Overland, 2009) and in the accelerated melting of both the Greenland icesheet (Velicogna, 2009; Khan et al., 2010; Rignot et al., 2011) and Antarctic ice sheets (Chen et al., 2009; Rignot et al., 2008, 2011; Velicogna, 2009); sea level rise (Rahmstorf 2007a,b; Rahmstorf et al., 2007; Nicholls et al., 2011); and release of trapped methane from the seabed (Westbrook et al., 2009; Shakova et al., 2010; although not yet globally significant Dlugokencky et al., 2009). The ‘worst case’ effects are compounding other changes more consistent with predictions including: changes in the distribution and abundance of marine species (Beaugrand & Reid, 2003; Beaugrand 2004, 2009; Beaugrand et al., 2003; 2010; Cheung et al. 2009, 2010, Reid et al., 2007; Johnson et al., 2011; Philippart et al., 2011; Schiel, 2011; Wassmann et al., 2011; Wernberg et al., 2011); changes in primary production (Behrenfeld et al., 2006; Chavez et al., 2011); changes in the distribution of harmful algal blooms (Heisler et al., 2008; Bauman et al., 2010); increases in health hazards in the oceans (e.g. ciguatera, pathogens; Van Dolah, 2000; Lipp et al., 2002; Dickey & Plakas, 2009); and loss of both large, longklived and small fish species causing widespread impacts on marine ecosystems, including direct impacts on predator and prey species, the simplification and destabilization of food webs, reduction of resilience to the effects of climate change (e.g. Jackson et al. 2001; Pauly et al., 1998; Worm & Myers, 2003; Baum & Myers, 2004; Rosenberg et al., 2005; Worm et al., 2006; Myers et al., 2007; Jackson, 2008; Baum & Worm, 2009; Ferretti et al., 2010; Hutchings et al., 2010; WardkPaige et al., 2010; Pinskya et al., 2011). • The magnitude of the cumulative impacts on the ocean is greater than previously understood Interactions between different impacts can be negatively synergistic (negative impact greater than sum of individual stressors) or they can be antagonistic (lowering the effects of individual impacts). Examples of such interactions include: combinations of overfishing, physical disturbance, climate change effects, nutrient runoff and introductions of nonknative species leading to explosions of these invasive species, including harmful algal blooms, and dead zones (Rabalais et al., 2001, 2002; Daskalov et al., 2007; Purcell et al., 2007; Boero et al., 2008; Heisler et al., 2008; Dickey & Plakas, 2009; Bauman et al., 2010; VaquerkSunur & Duarte, 2010); increased temperature and acidification increasing the susceptibility of corals to bleaching (Anthony et al., 2008) and acting synergistically to impact the reproduction and development of other marine invertebrates (Parker et al., 2009); changes in the behavior, fate and toxicity of heavy metals with acidification (Millero et al., 2009; Pascal et al., 2010); acidification may reduce the limiting effect of iron availability on primary production in some parts of the ocean (Shi et al., 2010; King et al., 2011); increased uptake of plastics by fauna (Andrady 2011, Hirai & Takada et al. 2011, Murray & Cowie, 2011), and increased bioavailability of pollutants through adsorption onto the surface of microplastic particles (Graham & Thompson 2009, Moore 2008, Thomson, et al., 2009); and feedbacks of climate change impacts on the oceans (temperature rise, sea level rise, loss of ice cover, acidification, increased storm intensity, methane release) on their rate of CO2 uptake and global warming (Lenton et al., 2008; Reid et al 2009). • Timelines for action are shrinking. The longer the delay in reducing emissions the higher the annual reduction rate will have to be and the greater the financial cost. Delays will mean increased environmental damage with greater socioeconomic impacts and costs of mitigation and adaptation measures. • Resilience of the ocean to climate change impacts is severely compromised by the other stressors from human activities, including fisheries, pollution and habitat destruction. Examples include the overfishing of reef grazers, nutrient runoff, and other forms of pollution (presence of pathogens or endocrine disrupting chemicals (Porte et al., 2006; OSPAR 2010)) reducing the recovery ability of reefs from temperaturekinduced mass coral bleaching (Hoeghk Guldberg et al., 2007; Mumby et al., 2007; Hughes et al., 2010; Jackson, 2010; Mumby & Harborne, 2010) . These multiple stressors promote the phase shift of reef ecosystems from being coralkdominated to algal dominated. The loss of genetic diversity from overfishing reduces ability to adapt to stressors. • Ecosystem collapse is occurring as a result of both current and emerging stressors. Stressors include chemical pollutants, agriculture runkoff, sediment loads and overkextraction of many components of food webs which singly and together severely impair the functioning of ecosystems. Consequences include the potential increase of harmful algal blooms in recent decades (Van Dolah, 2000; Landsberg, 2002; Heisler et al., 2008; Dickey & Plakas, 2009; Wang & Wu, 2009); the spread of oxygen depleted or dead zones (Rabalais et al., 2002; Diaz & Rosenberg, 2008; VaquerkSunyer & Duarte, 2008); the disturbance of the structure and functioning of marine food webs, to the benefit of planktonic organisms of low nutritional value, such as jellyfish or other gelatinousklike organisms (Broduer et al., 1999; Mills, 2001; Pauly et al. 2009; Boero et al., 2008; Moore et al., 2008); dramatic changes in the microbial communities with negative impacts at the ecosystem scale (Dinsdale et al., 2008; Jackson, 2010); and the impact of emerging chemical contaminants in ecosystems (la Farré et al., 2008). This impairment damages or eliminates the ability of ecosystems to support humans. • The extinction threat to marine species is rapidly increasing. The main causes of extinctions of marine species to date are overexploitation and habitat loss (Dulvy et al., 2009). However climate change is increasingly adding to this, as evidenced by the recent IUCN Red List Assessment of reforming corals (Carpenter et al., 2008). Some other species ranges have already extended or shifted polekwards and into deeper cooler waters (Reid et al., 2009); this may not be possible for some species to achieve, potentially leading to reduced habitats and more extinctions. Shifts in currents and temperatures will affect the food supply of animals, including at critical early stages, potentially testing their ability to survive. The participants concluded that not only are we already experiencing severe declines in many species to the point of commercial extinction in some cases, and an unparalleled rate of regional extinctions of habitat types (eg mangroves and seagrass meadows), but we now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation. Unless action is taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, overexploitation, pollution and habitat loss, the next globally significant extinction event in the ocean. It is notable that the occurrence of multiple high intensity stressors has been a prerequisite for all the five global extinction events of the past 600 million years (Barnosky et al., 2009).



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