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1、Threats to marine biodiversity Jon Nevilljonathan.nevill January 21, 2008Threats to marine ecosystems:In broad terms, the living inhabitants of the marine realm face five major threats: climate change: changes to oceanic temperatures, acidity and patterns of water movement (including currents, eddie
2、s and fronts), largely caused by increasing atmospheric carbon dioxide, as well as impacts from damage to the ozone layer; overfishing with attendant bycatch problems, both from commercial fishing, recreational fishing, illegal unregulated or unreported fishing (IUU), and ghost fishing. Ghost fishin
3、g refers to the continued effects of lost and abandoned fishing gear.; habitat damage largely caused by fishing gear, especially bottom trawling, but also including the effects of coastal development: destruction of coral reefs, mangroves, natural freshwater flows (and passage), coastal foreshores,
4、coastal wetlands and sometimes entire estuaries which all support coastal marine ecosystems; pollution (in-sea and land-based, diffuse and point source) including nutrients, sediments, plastic litter, noise, hazardous and radioactive substances; discarded fishing gear, microbial pollution, and trace
5、 chemicals such as carcinogens, endocrine-disruptors, and info-disruptors; and ecosystem alterations caused by the introduction of alien organisms, especially those transported by vessel ballast water and hull fouling. Amongst these five major threats to marine biodiversity, fishing has, until the p
6、resent time, been the most damaging on a global scale. The destructive impacts of fishing stem chiefly from overharvesting, habitat destruction, and bycatch. Over the coming century the threats posed by increasing atmospheric greenhouse gases pose huge dangers to the marine environment (Veron 2008,
7、Koslow 2007, Turley et al. 2006). At smaller scales, other threats (particularly pollution and habitat damage) are dominant at different localities. Coral reef, mangrove, estuarine, seagrass, mud-flat, and sponge-field habitats have been (and are being) extensively damaged. River passage, essential
8、for anadromous and diadromous species, has been impaired or destroyed around the globe.Overharvesting is probably as old as human civilization. There is evidence that ancient humans hunted many terrestrial animals to extinction (eg: Alroy 2001). Historically, fishing has rarely been sustainable (Pau
9、ly et al. 2002). On the global scene, modern fishing activities constitute the most important threat to marine biodiversity (Hiddink et al. 2008, Helfman 2007:8; MEA Millennium Ecosystem Assessment 2005a:67, 2005b:8, 2005c:12; Crowder & Norse 2005:183; Kappel 2005:275; Myers & Worm 2003; Pauly et al
10、. 2002; Renolds et al. 2002; Jackson et al. 2001; Leidy& Moyle1998 - noting contrary views from Gray 1997). Of all recently documented marine extinctions, the most common cause has been excessive harvesting activities (Malakoff 1997, Carlton et al. 1999, VanBlaricom et al. 2000).Fisheries in the dee
11、p sea have undoubtedly had the greatest ecological impact to date of all known threats (Thiel & Koslow 2001:9). Fishing was identified as the main threat to marine ecosystems in the northwest Atlantic over the period 1963-2000 (Link et al. 2002). The fisheries of the Bering Sea have long been recogn
12、ised as among the worlds best managed (Aron et al. 1993); however Greenwald (2006) in a study of the regions vertebrates, identified commercial fishing as the most important threat, followed by climate change, habitat degradation, ecological effects and pollution. Historically, the impacts of fishin
13、g activities, even when regulated by governments, have in many cases caused major, often irretrievable damage to marine ecosystems (Jackson et al. 2001, Ludwig et al. 1993). The benthic ecosystems of large areas of the ocean seabed have been destroyed or damaged (Watling 2005). The genetic effects o
14、f fishing may be substantial, yet are commonly ignored (Law & Stokes 2005). The failure of managers to learn from past mistakes appears to be a notable feature of the history of fisheries management (Mullon et al. 2005) in what Agardy (2000) has called the global, serial mismanagement of commercial
15、fisheries.In many sea areas, the weight of fish available to be harvested is calculated to be less than one tenth or even one one-hundredth of what it was before the introduction of industrial fishing. ( MEA 2005c:16)On the Australian scene, fishing activities appear to be the primary threat to fish
16、es (Pogonoski et al. 2002) and the second most important threat to marine invertebrates (Ponder et al. 2002) after habitat degradation.Overfishing is defined in this discussion as a level of fishing which puts at risk values endorsed either by the fishery management agency, by the nation in whose wa
17、ters fishing takes place, or within widely accepted international agreements. A point of critical importance in this regard is that a level of fishing intensity which successfully meets traditional stock sustainability criteria (for example fishing a stock at maximum sustainable yield) may well be c
18、onsiderably higher than a level of fishing intensity which meets criteria designed to protect marine biodiversity (Jennings 2007). The wide endorsement of the Convention on Biological Diversity 1992 implies that the latter level is the critical level by which overfishing should be measured.Amongst f
19、ishery scientists (and to lesser extent fishery managers) it is widely believed that “governance, and not science, remains the weakest link in the fisheries management chain” (Browman & Stergiou 2004:270). To a large extent fisheries managers, like bankers, do not learn the lessons of the past, they
20、 simply repeat them.The core impacts of climate change are caused by: an increase in the temperature of ocean waters - causing, for example, coral bleaching (Veron 2008); the increase in the acidity of ocean waters, causing a rising aragonite saturation horizon, particularly in the North Pacific and
21、 Southern Ocean - with resulting impacts on organisms using calcium carbonate body structures (Turley et al. 2006), and a reduction in ocean overturning circulation, risking, for example, impacts on deep ocean oxygen content (Koslow 2007). Important reviews of pollution in the marine environment are
22、 provided by: nutrients a general review: Rabalais (2005), Carpenter et a. (1998); in the Caribbean: Siung-Chang (1997); on shallow coral reefs: Koop et al. (2001); on the Great Barrier Reef: Alongi & McKinnon (2005); on the Gulf of Mexico: Rabalais et al. (2002) plastic litter Derraik (2002); Goldb
23、erg (1997); Koslow (2007); Gregory (1991) noise Cummings (2007); Firestone & Jarvis (2007); NRC (2005); Koslow (2007) radioactive waste Koslow (2007) armaments Koslow (2007) heavy metals Islam & Tanaka (2004); Hutchings & Haynes (2005) discarded fishing gear Matsuoka et al. (2005); Brown & Macfadyen
24、 (2007) microbial pollution Islam & Tanaka (2004) endocrine disruptors Lintelmann et al. (2003); Porte et al. (2006) info-disruptors Lurling & Scheffer (2007) other hazardous materials Islam & Tanaka (2004); Koslow (2007).Important papers on marine and estuarine habitat damage include: estuaries and
25、 rivers Ray (1996, 2004, 2005), Jackson et al. (2001), Blaber et a. (2000), Lotze et al. (2006), Collett & Hutchings (1978), Kappel (2005); Drinkwater & Frank (1994); impacts of bottom trawling Koslow (2007), Gray et al. (2006), Jones (1992), NRC (2002), Gianni (2004); coral ecosystems Aronson & Pre
26、cht (2006), Pandolfi et al. (2003), Gardiner et al. (2003), Hughes et al. (2003), McClanahan (2002), Jackson et al. (2001), McManus (1997); mangroves Duke et al. (2007), Alongi (2002), Ellison & Farnsworth (1996); seagrasses Orth et al. (2006), Duarte (2002); kelp Steneck et al. (2002), Dayton et al
27、. (1998).For a general introduction to the problem of alien species, see Mooney & Hobbs (2000), McNeely (2001), and Mack et al. (2000). General references on marine issues include Hewitt & Campbell (2007), Streftaris & Zenetos (2006), Carlton & Rutz (2005), Bax et al. (2003), and Rutz et al. (1997).
28、Threats and controls: Over the last thirty years, broad controls have been proposed or developed related to the five major threats. Controls can be categorised with threats (Table 1 below). Many nations have commendable statutes and policies; however implementation failures are widespread. Table 1.
29、Threats and controls: overview of general strategies: Threats Controls Overfishing and bycatch Restricted entry to fishery, catch quotas, limits or requirements on gear, limits on fishing seasons, limits on fishing areas, no-take areas, prohibitions on dumping or discarding gear. Attempts to reduce
30、or eliminate government subsidies contributing to fishing over-capacity. Control by flag States of high seas fishing particularly in regard to compliance with international and regional fishing agreements. Market-based fishery accreditation systems such as that of the Marine Stewardship Council. Gov
31、ernment control programs based on minimising ecosystem effects Surveillance and compliance programs including VMS. VMS refers to Vessel Monitoring Systems compulsory fitting of satellite tracking and reporting devices. Habitat damage Limits on gear, limits on fishing areas, no-take areas. Fixed moor
32、ing systems in sensitive (eg coral) environments. Surveillance and compliance programs. Land-based zoning schemes combined with project assessment and approval provisions aimed at minimising the loss of coastal habitat resulting from land-based developments. Special protection for high conservation
33、value estuaries. Zoning of key migration rivers to exclude dams, weirs and other impediments to fish passage. Protection of the catchment of high conservation value estuaries and rivers to maintain natural water flows and water quality.Threats Controls Climate change International agreements, such a
34、s those focussed on greenhouse gasses or chlorofluorocarbons or (eg: the Kyoto Protocol, Montreal Protocol) - and the implementation programs which follow, including incentives, prohibitions and market-based schemes aimed at reducing GG emissions. Pollution Controls focussed on fixed point sources,
35、mobile point sources and diffuse terrestrial sources including dumping and emissions to air and water . Controls on marine noise. Controls focused on specific pollutants, such as plastics or highly toxic or radio-active substances. Integrated coastal and river basin planning, including objectives to
36、 limit the passage of nutrients and other pollutants to the marine environment. Surveillance and compliance programs. Alien organisms Controls on ballast water and hull fouling based on risk minimisation rather than prevention. Import prohibitions relating to aquaculture stocks. Infestation monitori
37、ng and removal programs. Surveillance and compliance programs. Good general references covering threats and management options are Koslow (2007) and Norse & Crowder (2005).Three core concepts of modern marine managementAny overview of threat control programs would be incomplete without mentioning th
38、e evolution of three core concepts which underpin most national marine conservation policy frameworks, and many practical control programs: ecosystem-based fishery management (EBM); the precautionary principle (PP) and the closely-related precautionary approach (PA); and the strategic development of
39、 networks of marine protected areas (MPAs). Several fishery experts made comments during the eighteenth century to the effect that the resources of the ocean were so vast as to defy any possible damage from human activities. These views, although proved incorrect more than a century ago, still linge
40、r on, particularly in fisher cultures. Within government fishery agencies and academic circles, the need to take into account the effects of fishing for particular species on marine ecosystems has been accepted for several decades. Promotion of ecosystem-based management was a core feature of the FA
41、O Code of Conduct for Responsible Fisheries 1995. Although the concept is now embedded in international and national law, fishery agencies have generally been slow to incorporate EBM in fishery controls, usually citing the need for more research as the primary reason for the delay. The precautionary
42、 principle, and its softer version the precautionary approach, appeared in international discussions some decades ago. The precautionary principle appears in one of its many variations in the World Charter For Nature 1982, a resolution of the UN General Assembly, and was more formally endorsed in th
43、e Rio Declaration 1992 (United Nations Conference on Environment and Development)., and have been accepted, like EBM, into international and national law. Article 174 of the Treaty establishing the European Community requires, inter-alia, that Community policy on the environment be based on the prec
44、autionary principle. The principle was one of the core environmental principles contained in the Rio Declaration 1992 (UN Conference on Environment and Development) as well as the earlier World Charter for Nature 1982. One of countless similar definitions of the principle states it as follows: Where
45、 the possibility exists of serious or irreversible harm, lack of scientific certainty should not preclude cautious action by decision-makers to prevent such harm. Decision-makers needs to anticipate the possibility of ecological damage, rather than react to it as it occurs. Like EBM, use of the prec
46、autionary principle in practical control strategies has lagged behind its adoption in policy, not only in the EU but around the world. This remains the case, in spite of the prominence given to the principle on the FAO Code of Conduct. Marine protected areas were un-known in an era when it was gener
47、ally considered that the oceans needed no protection. However, as the damage to the marine environment became more widely understood, marine protected area programs have featured in international agreements as well as national conservation programs. The FAO Code of Conduct stresses the need to prote
48、ct critical habitat in aquatic environments, for example. One of the most widely quoted international statements calling for the acceleration of marine protected area programs around the world is that from the World Summit on Sustainable Development (WSSD Johannesburg 2002). The marine section of the WSSD Key Outcomes Statement provides basic benchmarks for the development of marine protected areas as well as other key issues: Encourage the application by 2010 of the ecosystem approach for the sustainable development of the oceans. O
