Transcript Document
Sustaining Aquatic Biodiversity Chapter 11 11-1 What Are the Major Threats to Aquatic Biodiversity? Concept 11-1 Aquatic species are threatened by habitat loss, invasive species, pollution, climate change, and overexploitation, all made worse by the growth of the human population. We Have Much to Learn about Aquatic Biodiversity We know fairly little about the biodiversity of the world’s marine and freshwater systems. • The greatest marine biodiversity occurs in coral reefs, estuaries and the deep ocean floor. • Biodiversity is higher near the coast and bottom because of habitat and food source variety. Human Activities Are Destroying and Degrading Aquatic Habitats Just remember H.I.P.P.C.O.!! Habitat destruction • Human activities have destroyed, disrupted or degraded a large proportion of the world’s coastal, marine and freshwater ecosystems. • Approximately 20% of the world's coral reefs have been destroyed. • We have destroyed more than 1/3 of the world’s mangrove forests for shipping lanes. • Freshwater aquatic zones are also affected • Dams and excessive water withdrawal from rivers/lakes Invasive Species, Population Growth, and Pollution Can Reduce Aquatic Biodiversity Invasive species are an increasing threat to marine and freshwater biodiversity. • Bioinvaders are blamed for about 2/3 of fish extinctions in the U.S. between 1900-2000. Almost half of the world’s Population lives on or near a coastal zone and 80% of ocean water. Pollution comes from land-based human activities. • Nitrates and phosphates mainly from fertilizers enter water • Leads to eutrophication • Toxic pollutants from industrial and urban areas Climate Change Is a Growing Threat Climate change as a result of global warming will cause sea levels to rise and aquatic biodiversity to be threatened. • Water too warm for coral reefs • Swamp some low-lying islands • Drown many highly productive coastal wetlands Overfishing and Extinction: Gone Fishing, Fish Gone Overfishing • About 75% of the world’s commercially valuable marine fish species are overfished or fished near their sustainable limits. • Big fish are becoming scarce. • Smaller fish are next. • Commercial extinction – so few exist that it is no longer profitable to continue • Bycatch – organisms caught unintentionally in nets • We throw away 30% of the fish we catch. Major Commercial Fishing Methods Used to Harvest Various Marine Species Trawler damage 11-2 How Can We Protect and Sustain Marine Biodiversity? Concept 11-2 We can help to sustain marine biodiversity by using laws and economic incentives to protect species, setting aside marine reserves to protect ecosystems, and using community-based integrated coastal management. Legal Protection of Some Endangered and Threatened Marine Species Why is it hard to protect marine biodiversity? • Human ecological footprint and fishprint are expanding • Much of the damage in the ocean is not visible • The oceans are incorrectly viewed as an inexhaustible resource • Most of the ocean lies outside the legal jurisdiction of any country Legal Protection of Some Endangered and Threatened Marine Species Laws, international treaties, and education can help reduce the extinction of marine species. • CITIES, ESA, etc. Since 1989 the U.S. government has required shrimp trawlers to use turtle exclusion devices. • Sea turtle tourism brings in almost three times as much money as the sale of turtle products. • “Dolphin Safe” tuna Case Study: Protecting Whales: A Success Story… So Far International Whaling Commission (IWC) After many of the world’s whale species were overharvested, commercial whaling was banned in 1986. • Annual harvest dropped from 42,000 to 1,300 Whale populations have rebounded so much that some countries are contemplating hunting again. Marine Sanctuaries Protect Ecosystems and Species Exclusive economic zones • A country’s offshore fishing zone extends 200 miles from the shore • This area is under their jurisdiction and is their responsibility High seas – beyond legal jurisdiction • Difficult to monitor and enforce international treaties Establishing a Global Network of Marine Reserves: An Ecosystem Approach Marine reserves areas of the ocean that are closed to commercial fishing, dredging, mining and waste disposal • Less harmful activities allowed • E.g., recreational boating and shipping Fully protected marine reserves make up less than 0.3% of the world’s ocean area. • Studies show that fish populations double, size grows by 30%, reproduction triples, and species diversity increases by 25%. Integrated Coastal Management – conservation efforts and methods need to customized to the specific region/ecosystem being protected. 11-3 How Should We Manage and Sustain Marine Fisheries? Concept 11-3 Sustaining marine fisheries will require improved monitoring of fish populations, cooperative fisheries management among communities and nations, reduction of fishing subsidies, and careful consumer choices in seafood markets. 11-3 How Should We Manage and Sustain Marine Fisheries? Maximum sustained yield (MSY) • The maximum that can be harvested without causing a population drop Optimum sustained yield (OSY) • Recalculates MSY taking into account the interactions with other species and allows for more room for error.