Environmental Problems

• Climate Change

• Pollution

• Overfishing

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Determining Causes of Earth’s Climate Change

• Paleoclimatology • Proxy data – indirect

evidence using natural recorders of climate variability– Sea floor sediments– Coral deposits– Glacial ice rings– Tree rings– Pollen – Historical documents

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Natural Causes of Climate Change

• Solar energy changes, Variations in Earth’s Orbit, Volcanic eruptions, Movement of Earth’s Plates

• Linked to Pleistocene Ice Age, Little Ice Age, Medieval Warm Period

• Recent change unprecedented– More likely result of human activity than

natural causes

Global Warming: Causes

• “Green house effect”

Fig. 15-40, p. 378

Global Warming: Causes

• Green house gases (chloroflourocarbons =CFCs, methane, CO2, water vapor)

• Increasing CO2

– Deforestation & burning fossil fuels

Table 16.01

Fig. 15-31, p. 326

Today – CO2 highest it has been in 10 million years

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Ice Core Data

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Global Warming• The 8 warmest years have occurred since 1998• Earth’s surface temperature has risen 0.8°C (1.4°F) in last

140 years.

Fig. 15-43, p. 380

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Changes in the OceansChanges in deep-water circulation • North Atlantic especially sensitive• Melting glaciers• Warmer surface waters

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Changes in the OceansPolar Ice Melting• Arctic amplification • Loss of more than

2 million square kilometers (800,000 square miles) of Arctic sea ice in last decade

• Loss of ice = enhanced warming due to lower albedo

Fig. 15-33, p. 327The North Pole 1996

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Changes in the OceansPolar Ice Melting• Arctic ice melting

affects polar bear survival.

• Food sources are dwindling for human Arctic dwellers.– Marine species migration

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Changes in the Oceans• Rising Sea Level –

already occurring • Main contributors:

– Melting of Antarctic and Greenland ice sheets

– Thermal expansion of ocean surface waters

– Melting of land glaciers and ice caps

– Thermal expansion of deep-ocean waters

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Global Sea Level Rise

The Maldives in the Indian Ocean – 80% pop. live only 1m above sea level

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Rising Sea Level

• Severely affect areas with gently sloping coastlines– U.S. Atlantic and Gulf Coasts

• Models predict rise between 0.5 and 1.4 meters (1.6 and 4.6 feet) by year 2100

• Affects coastal ecosystems like corals

Fig. 14-15, p. 340

Coral Bleaching Linked to Increased Temperatures

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Changes in the OceansOcean acidity increase• Some atmospheric

carbon dioxide dissolves in ocean water.– Acidifies ocean

• Threatens calcifying organisms– Coccolithophores– Foraminifers– Sea urchins– Corals

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Organisms Threatened by Increased Marine Acidity

Global Climate Change:Solutions?

• Alternative energy

Fig. 15-9, p. 355

Fig. 15-10a, p. 355

Fig. 15-10b, p. 355

Marine Pollution

• The introduction into the ocean by humans, substances that changes the physical, chemical or biological environment

Fig. 15-27, p. 367

Fig. 15-28, p. 368

Each year 240 million gallons of used motor oil are dumped in storm drains…22x the amount spilled by Exxon Valdez

Marine Pollution

• Bioamplification – even small amounts of pollutants can have large effects

• DDT example

DDT in water 0.000003 ppm

DDT in fish-eating birds (pelicans) 25

ppm

Concentration has increased 10 million times

DDT in small fish (minnows) 0.5 ppm

DDT in small zooplankton 0.04 ppm

DDT in large fish

(needlefish) 2 ppm

Stepped Art

Fig. 15-32, p. 371

Marine Pollution

• Eutrophication– Excess nutrients in water also lead to problems

• HABs

• Oxygen depletion

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Marine Fisheries • Commercial fishing• Most from continental

shelves• Over 20% from areas of

upwelling that make up 0.1% of ocean surface area

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Overfishing

• Fish from standing stock – the mass present in the ecosystem at any given time

• Overfishing – fish stock harvested too rapidly, juveniles not sexually mature to reproduce

• Reduction in Maximum Sustainable Yield (MSY)

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Exploitation Status of Marine Fish

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Overfishing • 80% of available fish

stock fully exploited, overexploited, or depleted/recovering

• Large predatory fish reduced

• Increased fishing effort, decreased stocks

Overfishing: Causes• Hard to estimate maximum sustainable

yield– Must know pop. size, growth & reproduction,

life span

• International waters

• Economic Needs

Bykill or By-catch

• Other species are accidentally caught

• Drift nets – banned in 1993

• “Dolphin-Safe Tuna”

• Turtle exclusion devises (TEDs)

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Purse Seine Net

Fig. 15-7a, p. 309

Fig. 15-7b, p. 309

Bycatch in a shrimp trawl

www.blueocean.org

TEDs

Fig. 15-26, p. 323

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Fisheries Management Effectiveness

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Fisheries Management

• Consumer choices in seafood

• Consume and purchase seafood from healthy, thriving fisheries– Examples: farmed seafood, Alaska salmon

• Ecosystem-based fishery management

• Avoid overfished or depleted seafood– Examples: tuna, shark, shrimp

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Seafood Choices

www.seafoodwatch.org