Chapter 9: Global Change

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