9.1: Stratospheric Ozone Depletion

• Stratosphere: Contains approximately 97% of the ozone in the atmosphere, and most of it lies between 9 and 25 miles (15–40 km) above Earth’s surface.

• Formation of Stratospheric Ozone

  • Ultraviolet radiation (uv) strikes an oxygen molecule, creating atomic oxygen.

  • Atomic oxygen can combine with oxygen molecules to form ozone.

• Ultraviolet radiation is subdivided into three forms:

  • UVA: It is closest to blue light in the visible spectrum and is the form of ultraviolet radiation that usually causes skin tanning.

  • UVB: It causes blistering sunburns and is associated with skin cancer.

  • UVC: It is found only in the stratosphere and is largely responsible for the formation of ozone.

• Ozone Layer: A belt of naturally occurring ozone gas that sits between 9 and 19 miles (15–30 km) above Earth and serves as a shield from the harmful ultraviolet B radiation emitted by the sun.

• Ozone: A highly reactive molecule and is constantly being formed and broken down in the stratosphere.

  • There are no natural reservoirs of chlorofluorocarbons (CFCs) or halocarbons (halons), but their chemical stability allows them to reach the stratosphere and degrade the ozone layer.

  • Chlorofluorocarbons: These are nonflammable chemicals that contain atoms of carbon, chlorine, and fluorine.

  • Halocarbons (halons): These are organic chemical molecules that are composed of at least one carbon atom with one or more halogen atoms; the most common halogens are fluorine, chlorine, bromine, and iodine.

Effects of Ozone Depletion

• A reduction in crop production

• A reduction in the effectiveness of the human body’s immune system

• A reduction in the growth of phytoplankton and the cumulative effect on food webs

• Climatic changes

• Cooling of the stratosphere

• Deleterious effects on animals

• Increases in cataracts

• Increases in mutations, since UV radiation causes changes in the DNA structure

• Increases in skin cancer

• Increases in sunburns and damage to the skin

Reducing Ozone Depletion

• Support legislation that reduces ozone-destroying chemicals in medical inhalers, fire extinguishers, aerosol hairsprays, wasp and hornet sprays, refrigerator and air conditioner foam insulation, and pipe insulation.

• Introduce tariffs on products produced in countries that allow the use of chlorofluorocarbons (CFCs).

• Offer tax credits or rebates for turning in old refrigerators and air conditioners.

• Use helium, ammonia, propane, or butane as a coolant alternative to HCFCs (hydrochlorofluorocarbons) and CFCs.

9.2: The Greenhouse Effect

• When sunlight strikes Earth’s surface, some of it is reflected back toward space as infrared radiation (heat).

• Greenhouse gases absorb this infrared radiation and trap the heat in the atmosphere.

9.3: Increases in Greenhouse Gases

Greenhouse Gases by Source

• Agriculture: Mostly comes from the management of agricultural soils.

• Commercial and residential buildings: On-site energy generation and burning fuels for heat in buildings or cooking in homes

• Energy supply: The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions.

• Industry: Primarily involves fossil fuels burned on-site at facilities for energy; cement manufacturing also contributes significant amounts of CO2 gas

• Land use and forestry: It includes deforestation of old-growth forests (carbon sinks), land clearing for agriculture, strip-mining, fires, and the decay of peat soils

• Transportation: It involves fossil fuels that are burned for road, rail, air, and marine transportation.

• Waste and wastewater: Landfill and wastewater methane (CH4), and incineration as a method of waste management.

Greenhouse Gas Emissions by Gas

• Carbon dioxide (CO2): It is an important heat-trapping (greenhouse) gas, and is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions.

• Agricultural activities, waste management, and energy use all contribute to methane emissions.

• Fertilizer use is the primary source of nitrous oxide emissions.

• Fluorinated gases: Industrial processes, refrigeration, and the use of a variety of consumer products all contribute to this gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

• Black carbon (soot): It is a solid particle or aerosol, not a gas, but it also contributes to the warming of the atmosphere.

9.4: Global Climate Change

• The world’s oceans contain more carbon dioxide than the atmosphere.

• Atmospheric temperatures, cloud cover, surface albedo, and water vapor cause pole-wide warming.

  • The north and south poles are warming faster because of energy in the atmosphere that is carried to the poles through large weather systems.

• Ocean currents carry heat around the Earth.

  • As the oceans absorb more heat from the atmosphere, sea surface temperatures rise and ocean circulation patterns change.

  • As the oceans store a large amount of heat, even small changes in these currents can have a large and lasting effect on the global climate.

• Air temperatures today average 5°F to 9°F (3°C to 5°C) warmer than they were before the Industrial Revolution.

  • Higher average air temperatures may increase the frequency or severity of storms, surface water/groundwater inputs, sedimentation in bodies of water, flooding and associated water runoff, and aquifer recharge.

• Global warming could completely change estuaries and coastal wetlands.

  • Sea-level rise threatens to inundate many coastal wetlands, threatening biota that cannot move inland due to coastal development.

• The UN estimates that 150 million people will need to be relocated worldwide by 2050 due to coastal flooding, shoreline erosion, and agricultural disruption.

• The total surface area of glaciers worldwide has decreased 50% since the end of the 19th century.

• The main ice-covered landmass is Antarctica at the South Pole, with about 90% of the world’s ice and 70% of its freshwater.

  • If all of the Antarctic ice melted, sea levels around the world would rise about 200 feet (60 m).

• Greenhouse gases trap solar radiation in the Earth’s atmosphere, making the climate warmer.

• Due to global warming, mosquitoes have more places to breed, which increases malaria, dengue fever, Zika virus, and yellow fever rates.

  • Warmer water may spread amoebic dysentery, cholera, and giardia because it increases bacterial activity.

• Higher air temperatures have been proven to result in higher incidences of heat-related deaths caused by cardiovascular disease, heat exhaustion, heat stroke, hyperthermia, and diabetes.

• Arctic fauna will be the most affected. The food webs of polar bears that depend on ice floes, birds, and marine mammals will be drastically affected.

• The movement of tectonic plates causes volcanoes and mountains to form, which can also contribute to changes in the climate

• Volcanic gases that reach the stratosphere have a long-term effect on climate.

• The fluctuations in the solar cycle impact Earth’s global temperature by ~0.1°, slightly hotter during solar maximums and slightly cooler during solar minimums.

• As rivers and streams warm, warm-water fish are expanding into areas previously inhabited by cold-water species.

• The Arctic region is a large natural source of methane.

  • Arctic methane release, caused by melting glaciers, creates a positive feedback loop because methane is a greenhouse gas.

• Sea levels have risen 400 feet (120 m) since the peak of the last ice age approximately 18,000 years ago.

  • From about 13,000 years ago to the start of the Industrial Revolution, sea levels rose 0.1 to 0.2 mm per year. Since 1900, sea levels have risen about 3 mm per year.

• The amount of energy absorbed and stored by the oceans has an important role in the rise of sea levels due to thermal expansion.

• Ocean acidification: It occurs when atmospheric carbon dioxide reacts with seawater to form carbonic acid,

• Kyoto Protocol (2005): A plan created by the United Nations to reduce the effects of climate change, which results in a reduction in the pH of ocean water over an extended period of time.

• Montreal Protocol (1987): An international treaty designed to phase out the production of substances that are responsible for ozone depletion.

• Paris Agreement (2016): It deals with greenhouse gas emissions and mitigation.

  • The goal is to keep global temperature rise below 2°C above pre-industrial levels while each country determines its own plans to mitigate global warming.

9.5: Biodiversity and Invasive Species

• Plants are initially more susceptible to habitat loss than animals. This occurs for several reasons, as follows:

  • Plants cannot migrate.

  • Plants cannot seek nutrients or water.

  • Seedlings must survive, and they are grown in degraded conditions.

  • The dispersal rates of seeds are slow events

• Animals can cope with habitat destruction by migration, adaptation, and/or acclimatization. Migration depends upon:

  • access routes or corridors;

  • the magnitude and rate of degradation;

  • the organism’s ability to migrate; and

  • the proximity and availability of suitable new habitats.

• Adaptation: The ability to survive in changing environmental conditions.

  • Adaptation depends upon:

    • birth rate;

    • gene flow between populations as a function of variation;

    • genetic variability;

    • population size;

    • the length of generation; and

    • the magnitude and rate of degradation.

• Acclimatization: The process by which an individual organism adjusts to a gradual change in its environment allowing it to maintain performance across a range of environmental conditions.

  • Acclimatization depends upon:

    • physiological and behavioral limitations of the species; and

    • the magnitude and rate of degradation.

Invasive Species

• Invasive species: These are animals and plants that are transported to any area where they do not naturally live.

• Characteristics of Invasive Species

  • Abundant in native range

  • Broad diet

  • High dispersal rates

  • High genetic variability

  • High rates of reproduction

  • Living in close association with humans

  • Long-lived

  • Pioneer species

  • Short generation times

  • Tolerant of a wide range of environmental conditions

  • Vegetative or clonal reproduction

• Examples of Invasive Species

  • Dutch elm disease is transmitted to elm trees by elm bark beetles — killing over half of them elm trees in the northern US.

  • European green crabs found their way into the San Francisco Bay area in 1989 threatening commercial fisheries.

  • Water hyacinth is an aquatic plant, introduced to the United States from South America.

    • It forms dense mats, reducing sunlight for submerged plants and aquatic organisms, crowding out native aquatic plants, and clogging waterways and intake pipes.

  • Zebra mussels can attach to almost any hard surface—clogging water intake and discharge pipes, attaching themselves to boat hulls and docks, and even attaching to native mussels and crayfish.

9.5: Endangered Species

• Endangered Species: A species considered to be facing a very high risk of extinction in the wild.

• Factors are taken into account for being labeled “endangered:”

  • Breeding success rate

  • Known threats

  • The net increase/decrease in the population over time

  • The number of animals remaining in the species

• Arguments for protecting endangered species

  • Maintaining genetic diversity

  • Maintaining keystone species

  • Maintaining indicator species

  • Preserving the endangered species’ aesthetic, ecological, educational, historical, recreational, and scientific value

  • Preserving the yet-to-be-discovered value of certain endangered species

• Characteristics That Have Contributed to Endangerment

  • Compete for food with humans

    • African penguins

  • High infant mortality

    • Leatherback turtles

  • Highly sensitive to changes in environmental conditions

    • Cotton-top tamarins

  • Hunting for sport

    • Passenger pigeons, blue whales, Bengal tigers

  • Introduction of nonnative invasive species

    • Bandicoots threatened by cats that were introduced by Europeans

  • Limited environmental tolerance ranges

    • Frogs, whose eggs are sensitive to water pollution, temperature changes, and the destruction of wetlands

  • Limited geographic range

    • Pandas

  • Long or fixed migration routes

    • Salmon in the Pacific Northwest that have been driven to extinction because of dam construction, logging, and water diversion

  • Loss of habitat

    • Red wolves. Whooping cranes

  • Low reproductive rates

    • Whales, elephants, and orangutans.

  • Move slowly

    • Desert tortoises

  • No natural predators, which makes them vulnerable as they lack natural defensive behaviors and mechanisms

    • Dodo birds, Steller’s sea cows, sea otters

  • Not able to adapt quickly

    • Polar bears

  • Possess characteristics sought after for commercial purposes

    • Sharks, elephants, rhinoceros’ horns. gorillas

  • Require large amounts of territory

    • Tigers

  • Small numbers of the species, which limits genetic diversity

    • Tigers

  • Specialized feeding behaviors and/or diet

    • Pandas (Bamboo)

  • Spread of disease by humans or livestock

    • African wild dogs

  • Superstitions

    • Aye ayes—some people native to Madagascar believe that aye ayes bring bad luck, and therefore kill them.

Maintaining Biodiversity

• Creating and expanding wildlife sanctuaries

• Establishing breeding programs for endangered or threatened species

• Managing habitats and monitoring land use

• Properly designing and updating laws that legally protect endangered and threatened species.

• Protecting the habitats of endangered species through private and/or governmental land trusts

• Reintroducing species into suitable habitats

• Restoring compromised ecosystems

• Reducing nonnative and invasive species