Unit 9 Test Flashcards
The Greenhouse Effect
principal greenhouse gases are water vapor (H2O), carbon dioxide (CO2), and methane, but several other gases (mainly pollutants), such as nitrous oxide, ozone, chlorofluorocarbons (CFCs), and hydrofluorocarbons (HFCs) have some amount of greenhouse effect as well.
several human activities are responsible for the release of these gases in greater quantities than would naturally occur without us.
have recently reached the unavoidable consensus that the global climate is undergoing a shift that is almost certainly in large part due to these human contributions: an idea referred to simply as climate change
CLIMATE CHANGE
Scientists use very sophisticated computer models and make several thousand meteorological observations each day to monitor the daily temperature of the Earth’s atmosphere. Over the last several years, their observations have shown that there has been a slow but steady rise in the Earth’s average temperature. According to NASA, 2020 tied with 2016 as the warmest year on record (and 2021 tied with 2018 as the sixth warmest year on record). Other qualified scientists have carefully documented a decrease in the size of glaciers and ice sheets, a slight rise in the average ocean level, and more severe rainstorms. In response to these phenomena, the Intergovernmental Panel on Climate Change (IPCC) gathered hundreds of scientists from around the world to study these problems. In a 2013 report, the IPCC stated that most of the observed increase in the global average temperature since the mid-20th century is very likely (greater than 95 percent) due to the observed increase in anthropogenic greenhouse gas concentrations. The three major gases are carbon dioxide (from pre- industrial levels of 280 ppm to 400 ppm in 2016), methane (from preindustrial levels of 715 ppb to 1,840 ppb in 2016), and nitrous oxide (from preindustrial levels of 270 ppb to 328 ppb in 2016). These gases absorb the infrared heat radiating from the Earth and thus heat the lower atmosphere. This warming is in addition to the normal warming of the atmosphere by the greenhouse effect.
Global warmnig potential
The impact of a particular greenhouse gas on global climate change can be thought of in terms of its global warming potential (GWP). Carbon dioxide, which has a GWP of 1, is used as a reference point for the comparison of the impacts of different greenhouse gases on global climate change. Chlorofluorocarbons (CFCs) have the highest GWP, followed by nitrous oxide, and then methane.
Water vapor as a greenhouse gas
It should also be mentioned that while water vapor is a greenhouse gas and even accounts for the largest percentage of the greenhouse effect, it doesn’t contribute significantly to global climate change, because it has a short residence time in the atmosphere (an average of about nine days compared to years or centuries for other greenhouse gas molecules), and its levels have remained consistent for some time. However, water does respond to and amplify the effects of other greenhouse gases.
Global warming effects
The increase in the Earth’s temperature will lead to a variety of changes to the Earth. Physical changes on Earth include continued rising temperatures, further melting of glaciers, ice sheets, and permafrost, changes in precipitation patterns (with wet areas getting more precipitation and dry areas getting less precipitation), an increase in the frequency and duration of storms, an increase in the number of hot days, and a decrease in the number of cold days.
While it’s clear that rising air and surface temperatures have widespread effects on the biosphere, it’s also true that ocean temperatures are increasing due to the increase in greenhouse gases in the atmosphere and the greenhouse effect they produce. The most far-reaching consequence of this is that the thermal expansion of water (warm water is less dense than cooler water, and therefore takes up more space) is one of the factors contributing to rising sea levels (along with the melting of glaciers and ice sheets mentioned above). Ocean warming will also likely cause changes in coastlines, ocean currents, sea surface temperatures, tides, the sea floor, and weather.
Complicating the picture of oceanic effects is the phenomenon of ocean acidification, the decrease in pH of the oceans that’s primarily another effect of the increased carbon dioxide concentrations in the atmosphere due to the burning of fossil fuels, vehicle emissions, and deforestation. As more carbon dioxide is released into the atmosphere, the oceans absorb a large part of that carbon dioxide. Dissolving CO2 increases the hydrogen ion concentration (as shown below), and causes ocean water to become more acidic.
Climate change will also affect biota. While there will be increased crop yields in cold environments, this is likely to be offset by loss of croplands as other areas suffer droughts and higher temperatures. Cold-tolerant species will need to migrate to cooler climates or they may become extinct. As equatorial-type climate zones spread north and south into what are currently subtropical and temperate climate zones, pathogens, infectious diseases, and any associated vectors will spread into these areas (where these diseases have not previously been known to occur). Entire coastal populations and ecozones will also be displaced by the rising oceans.
Marine ecosystems will also be affected. The change in sea level will have effects: some positive (for example, in newly created habitats on newly- flooded continental shelves) and some negative (for example, in deeper communities that may no longer fall within the photic zone of seawater). But the effects of ocean warming are likely to be even more drastic. Some habitats will be damaged or lost; some species are likely to adapt through metabolic and/or reproductive changes; and, as with sea levels, ocean warming may have positive effects on some habitats and organisms as well.
ocean acidification: coral
has and will continue to have tangible effects on ocean biota as well. Some species are experiencing reproductive and metabolic changes, just as with ocean warming; and the greatest effects of acidification can be seen in organisms that make use of calcification (as in shells): for example, corals.
coral reefs are structures found in warm, shallow tropical waters that represent diverse and ecologically crucial ecosystems. Coral reefs are created by small marine animals (called cnidarians), which are involved in mutualistic relationships with photosynthetic algae called zooxanthellae. Reefs provide local populations with a great variety of seafood and are popular recreational areas for humans.
Ocean acidification damages corals by decreasing their ability to calcify (due to loss of calcium carbonate), making it difficult for them to form shells. When you put this together with coral bleaching, the world’s coral reefs are under severe threat.
coral bleaching
what happens when coral polyps expel the symbiotic algae that live in their shells and are vital to their health—the algae provide up to 90 percent of the corals’ energy! Once a coral bleaches, it continues to live but begins to starve. Some corals recover, but many don’t. The leading cause of coral bleaching is rising water temperatures, but the list of contributing factors also includes:
increased sunlight exposure
increased sedimentation (due to silt runoff)
bacterial infections
increased or decreased salinity
herbicides
exposure (as in extremely low tides)
mineral dust carried in dust storms caused by drought
pollutants such as those commonly found in sunscreens
ocean acidification
oil and chemical spills
oxygen starvation caused by increase in zooplankton after overfishing
In many areas of the world, pollution, climate change, and exploitation have led to severe and irreversible damages to these reefs.
global climate change: larger patterns of climate, winds
Winds generated by atmospheric circulation help transport heat throughout the Earth. Climate change may change the circulation patterns of wind, because the temperature changes may impact Hadley cells and the jet stream. And the winds in turn affect the oceanic currents, which carry heat in the water just as the winds do in the air. When these currents change, it will likely have a great impact on the climate in many places, especially coastal regions.
global climate change: polar regions
The Earth’s polar regions are showing faster response times to global climate change, because ice and snow in these regions reflect the most energy back out to space, leading to a positive feedback loop. As the Earth warms, this ice and snow melts, meaning less solar energy is radiated back into space and instead is absorbed by the Earth’s surface. This in turn causes more warming of the polar regions. In addition, the melting sea ice and thawing tundra release greenhouse gases like methane, which add even more to the global change! And to top it all off, the polar regions represent some of the more delicate ecosystems on the planet, which recover the most slowly from disruptions. One consequence of the loss of ice and snow in polar regions, for example, is the effect on species that depend on the ice for habitat and food. The species that are adapted to the coldest places on Earth may not have anywhere to displace to when even those places become warmer.
climate change: soil
Climate change will also probably affect soil in many places planetwide, since changes in temperature and rainfall can impact the viability of soil and potentially increase erosion—which can then change the makeup of the soil as well.
climate change: human health
Human health will show additional deaths from water- and insect-borne diseases. More frequent heat spells will endanger the very young and old. It is very likely that commerce, transport facilities, and coastal settlements will be disrupted by ocean level changes and stronger, more frequent storms.
Ozone layer
Stratospheric ozone absorbs UV light from the sun and therefore protects life on our planet, and is thus functionally very different from tropospheric ozone (which is a powerful respiratory irritant and precursor to secondary air pollutants). Ozone in the stratosphere provides us with a much-needed defense against ultraviolet radiation. The ozone layer is responsible for blocking about 95 percent of the sun’s ultraviolet radiation (UV), thus protecting surface-dwelling organisms from UV damage. Ozone is naturally created by the interaction of sunlight and atmospheric oxygen. The simplified reaction is
O2 + UV (sunlight) O + O O + O2 O3
Ozone layer hole
As early as the mid-1950s, a thinning of the ozone layer above the Antarctic was observed. In the 1970s, atmospheric scientists hypothesized, and later proved, that declining stratospheric ozone levels were due to a group of man- made chemicals known as chlorofluorocarbons (CFCs). Invented in the 1930s, CFCs and many other related compounds (e.g., halons and hydrochlorofluorocarbons) were used in items such as propellants, fire extinguishers, and cans of hairspray.
Once released, CFCs migrate to the stratosphere through atmospheric mixing (they are very stable, which allows them to survive through the rise). In the
upper stratosphere, intense UV radiation breaks the CFC molecules apart and releases chlorine atoms that form chlorine monoxide (ClO) while converting O3 to O2. Let’s take a look at that reaction.
Cl + O3 ClO + O2
During the winter months, chlorine monoxide is concentrated on ice crystals that form in and around the Antarctic polar vortex. In early spring, the returning warmth of the sun frees the chlorine from the chlorine monoxide where it destroys more ozone. The reaction that frees the chlorine from chlorine monoxide is seen at the top of the next page.
ClO + O Cl + O2
Ozone loss is greatest in the spring as the chlorine breaks down ozone into O2. Remember that chlorine acts as a catalyst; it is not changed by its
reaction with ozone and it can help break down another O3 molecule
immediately. As the air continues to warm, the natural production of ozone increases as more sunlight catalyzes the combination of oxygen back into ozone. This occurs in January and February (Antarctica’s summer).
The Antarctic continent is the area exposed to the greatest amount of UV radiation, but prevailing winds can carry the ozone-depleted air to South America, Australia, and southern Africa. In 2006, the area of ozone thinness was over 26 million square kilometers. Reduced levels of ozone have been documented over the Arctic and even over some midlatitude regions.
effects of ozone hole/loss of ozone
The loss of ozone has serious implications for the Earth’s ecosystems as well as for human health. The increased number of UV rays that reach the Earth through the thin ozone layer can kill phytoplankton and other primary producers. The decrease in primary productivity of both marine and terrestrial ecosystems lowers the amount of available fish and crops. Human health issues from increased exposure to UV rays include eye cataracts, skin cancers, and the weakening of our immune systems.
HIPPCO (human factors that can cause extinction and decrease biodiversity)
Habitat destruction/fragmentation Invasive species
Population growth
Pollution
Climate change Overharvesting/overexploitation
Invasive species
introduced species (non-native species) that are successful where they’re introduced. They can sometimes be beneficial, but they tend to be labeled invasive when their impact alters the environment they are introduced to—by outcompeting native species, using up resources or prey, or physically altering the habitat—in ways that threaten native species. In Chapter 5 we mentioned that invasive species tend to be r-selected generalists, while the species most adversely affected by invasives tend to be K-selected specialists. The ability of generalists to adapt gives them an advantage in new surroundings, and the characteristics of r-selected species (populations below the carrying capacity of their environment, small body size, short lifespans, early maturation and reproduction, many offspring at once) mean there’s a good chance that at least some members will survive to establish a foothold there.
habitat loss/fragmentation
numerous causes of habitat loss, including global climate change (via changes in temperature, precipitation, and sea level rise), ocean warming and acidification, pollution, and human development. Habitat fragmentation occurs when large habitats are broken into smaller, isolated areas, which can happen as a result of the construction of roads and pipelines, clearing for agriculture or development, and logging, for example. The scale of habitat fragmentation that has an adverse effect on the inhabitants of a given ecosystem will vary from species to species within that ecosystem, so some species may suffer from habitat loss in the very same place where other species are still thriving. Of course, species loss affects food webs, and may eventually be the factor that means the habitat can no longer support other species as well.
habitat loss/fragmentation: wetlands
some of the most fragile and easily disrupted. They provide a wealth of ecosystem services: wetlands improve water quality by basically acting as giant water filters; they are natural sources of methane; they are a source of biodiversity and a habitat for diverse wildlife; and they provide protection from floods as reservoirs for floodwater to drain to. Given their importance, it’s all the more problematic that wetlands are at risk on many fronts. Threats to wetlands include overfishing, pollutants from agriculture and industrial waste, and habitat destruction and fragmentation due to commercial development and dam construction.
other than habitat/loss from fragmentation, also monoculture and domestication
Agriculture—specifically monoculture —has expanded the range of just a few plant species enormously, and diminished that of many others in the balance. Animal species have been affected as well. Some animal species have been somewhat or completely domesticated and many of those are now managed for economic returns (such as with honeybee colonies and domestic livestock). Domestication (whether as pets or livestock) can have a negative impact on the biodiversity of a species—inevitably, humans will breed for characteristics that are desirable or useful to us, which often goes counter to what would naturally increase or maintain high biodiversity.
classifications for endangered species populations
The International Union for Conservation of Nature (IUCN) evaluates the conservation status of plant and animal species. A species is designated as critically e ndange re d if the species is under a very high risk of extinction; endangered if the species is likely to become extinct; and vulnerable if the species is likely to become endangered if no action is taken. Species assigned to any one of these three categorizations are considered threatened species
background extinction rate
Extinctions have happened throughout the Earth’s history. This natural rate of extinction—occurring apart from widespread events—is called the background extinction rate. Knowledgeable scientists estimate that the current extinction rate is between 50 and 500 times higher than in the past, likely due to human influence. Extinctions can happen anywhere in the world, but the rates are particularly high in the tropics (mostly on mountains and islands, which are home to isolated small populations that are especially vulnerable to both natural and human-caused changes to their environments).
factors that cause species to become endangered.common factors between endangered species
Being extensively hunted, having a limited diet that becomes less available, being outcompeted by invasive species, or having specific and limited habitat requirements in an area where those are getting harder to fulfill. Not all species will be in danger of extinction when exposed to the same changes in their ecosystem. Species that are able to adapt to changes in their environments—or that are able to move to new environments —are much less likely to face extinction.
Thus, the species that are most endangered have several factors in common: they require large ranges of habitat to survive, have low reproductive rates, have specialized feeding habits, have some sort of value to humans (medicinal or food), and have low population numbers.
human role in extinction of species
Humans play a major role in the extinction of species because of our destruction of animal and plant habitats. Poverty and rapid population growth cause people to use destructive practices, such as slash-and-burn farming, that destroy species’ habitats. When we build roads or cities, habitats are lost or fragmented; this fragmentation may prevent the free movement of a species to find mates or escape danger, or it may reduce the area a species has for all the activities of its life cycle below a critical threshold. Finally, we cause habitat degradation by adding pollutants to the environment. Other factors that can contribute to extinction are invasive species and the direct hunting or overexploitation of a species or desired resources. Dr. Norman Myers coined the term biodiversity hot spot to describe a highly diverse region that faces severe threats and has already lost 70 percent of its original natural habitat by area.
Montreal Protocol
The loss of ozone was driven by increasing CFCs and related chemicals released during human use and rising to the stratosphere. But fortunately, there are several methods to manage the amounts of CFCs we release. In 1987, the Montreal Protocol was signed by more than 146 nations. The protocol calls for the worldwide end of CFC production. The United States stopped production in 1995. Since the institution of the Montreal Protocol, the release of ozone- depleting chemicals has been reduced by 95 percent. There are many nations that still rely on CFCs, though work is being conducted to develop safe and effective substitutes. Hydrofluorocarbons (HFCs) are one such replacement, but some are strong greenhouse gases. Though the problem still exists, a global recovery is underway. Ozone levels are now beginning to increase
amended in Copenhagen (1992) to include other key ozone-depleting chemicals.
Kyoto Protocol
1997
Required the participating 38 developed countries to cut their greenhouse gas emissions back to 5% below 1990 levels. While the United States signed the agreement, it did not ratify the agreement. As a result, the United States is not bound to abide by the Kyoto Protocol
mitigating biodiversity loss
First, we can conserve habitats by requiring that large tracts of land be set aside and protected from human activity. In these protected habitats, organisms can find their niches and survive without risk of human interference. National parks and animal sanctuaries are two examples of protected habitats. This protection will slow the loss of species, and in some cases, allow species to recover and gain numbers. Making it illegal to trade in specific organisms means that those organisms will not be hunted or collected. Obviously, legislation is an important tool, and theEndangered Species Act, which requires its agency to designate which species are threatened and endangered and codifies the protection of those species and their habitats, has been key to this effort
