The Atmosphere, Climate Change, Biodiversity, and Sustainable Use

Flashcards testing core concepts on the atmosphere, climate change, greenhouse gases, deforestation, alien species, biodiversity loss, and sustainable resource management.

What are greenhouse gases (GHGs), and what are the two main examples?

Greenhouse gases are gases which trap heat in the atmosphere. The two main GHGs are carbon dioxide ($CO_2$) and methane ($CH_4$).

How are emissions defined in environmental science?

Emissions are released gases which are usually harmful to the environment.

What is the greenhouse effect?

The warming of the surface of the Earth by greenhouse gases trapping heat in the atmosphere.

What role does the natural greenhouse effect play on Earth?

When greenhouse gases are in balance, they regulate Earth's temperature and enable life on Earth.

What occurs during the enhanced greenhouse effect?

When excessive greenhouse gases are emitted, they trap too much heat in the atmosphere, resulting in global warming.

What is global warming?

The rise in Earth's average temperature as a result of the enhanced greenhouse effect.

What is a carbon sink?

Any natural system (soil, water or plant) which absorbs and stores carbon dioxide ($CO_2$).

How is a carbon footprint defined?

The amount of carbon dioxide released into the air because of individual or group energy needs.

What is ozone depletion?

Reduction in the concentration of ozone in the ozone layer in the stratosphere (upper atmosphere).

What is deforestation?

The destruction of natural forests through human activities.

What is desertification?

The process by which fertile land becomes desert.

What is the percentage composition of gases in Earth's atmosphere?

Earth's atmosphere consists of $78\%$ nitrogen ($N_2$), $21\%$ oxygen ($O_2$), and $1\%$ remaining gases, mainly carbon dioxide ($CO_2$) and other trace amounts.

What are the main sources of carbon dioxide ($CO_2$) emissions listed in the lecture notes?

Cellular respiration (exhaled $CO_2$), decomposition of dead plants and animals, burning of fossil fuels for electricity or transport, chemical reactions in the cement and fertilizer industries, and veld fires or domestic wood burning.

What proportion of atmospheric methane ($CH_4$) is caused by human activities?

Human activities are responsible for over $60\%$ of total methane in the atmosphere.

What are the main natural and human sources of methane ($CH_4$) emissions?

Natural anaerobic decomposition in wetlands, melting polar ice and permafrost, decomposing marine organisms in seawater, intensive agriculture (decomposing dung/compost, ruminant gas), and industrial/mining processes (refining fossil fuels, drilling/fracking).

What are ruminants and how do they contribute to methane emissions?

Ruminants are animals with two stomachs (mostly cattle) that release methane gas into the atmosphere.

What effects does global warming have on temperature, weather, and sea levels?

Sharply rising temperatures cause more heat waves alternating with extreme weather like powerful storms, and rising sea levels cause coastal flooding that can submerge coastal cities.

How does global warming impact rainfall patterns, food production, and oceans?

Rainfall patterns shift (turning wet areas into deserts and flooding dry ones), crop failures increase food insecurity, warmer seawater kills shallow coral reefs, and increased $CO_2$ forms carbonic acid that acidifies seawater and weakens exoskeletons.

What statistics are given regarding desertification globally and in South Africa?

$33\%$ of land globally is becoming desert (putting one billion people at risk of famine), and $90\%$ of South Africa is classified as desert or semi-desert.

What percentage of total global greenhouse gas emissions is estimated to come from deforestation?

Deforestation is estimated to contribute $20\%$ of the total global greenhouse gas emissions.

What are the key reasons given for deforestation and desertification?

Land clearance (farming/urban development), commercial logging, removal of commercial plantations, mining operations, cutting trees for fuel (firewood/charcoal), traditional medicine harvesting (bark/roots), forest fires, and acid rain.

How does deforestation lead to an increase in atmospheric carbon dioxide ($CO_2$)?

Forests act as natural carbon sinks that absorb $CO_2$ during photosynthesis. When forests are destroyed, $CO_2$ remains in the atmosphere instead of cycling into humus and soil.

Which rainforest is identified as Africa's largest carbon sink?

The rainforests of the Congo Basin.

How does deforestation contribute to an increase in atmospheric methane ($CH_4$)?

Livestock (goats, sheep, cows) in cleared areas produce $CH_4$, and termite populations feeding on dead trees release large quantities of $CH_4$.

What are the non-greenhouse consequences of deforestation listed in the notes?

Soil degradation (nitrogen loss, wind and water erosion), more frequent flooding/mudslides, accelerated desertification, and species extinction (estimated 50,000 species annually).

What are exotic plants, and why do invasive alien plants out-compete indigenous species?

Exotic plants are imported from another ecosystem and established in a new habitat. They out-compete indigenous plants because they lack natural enemies and diseases in the new environment.

How do alien plantations negatively impact soil, water, and livestock pastures?

They deplete the water table with deep roots, leach nutrients due to incomplete decomposition, alter soil pH to make it acidic, and invade pastures with inedible or poisonous plants.

What are five common examples of invasive plants in South Africa?

The Jacaranda, Water hyacinth, The pine tree, The wattle tree, and The eucalyptus tree.

What is biodiversity?

Biodiversity is the biological diversity, range, or variety of life forms in a particular area.

What is the greatest cause of a loss of biodiversity?

Habitat destruction.

How do golf estates and luxury developments contribute to loss of biodiversity?

They destroy and fragment habitats, introduce exotic grasses (like kikuyu) and alien plants, deplete the water table, use high amounts of fertilizer (causing eutrophication), and generate pollution.

What is the definition of sustainable use?

Sustainable use is the use of resources to fulfil human needs, while ensuring there is a sufficient supply for future generations.

What is the scientific name, medicinal use, and sustainable measure for Devil's claw?

Scientific name: Harpagophytum procumbens. Uses: relieve pain, inflammation, arthritis, lower back pain, and digestive disorders. Sustainable measure: harvest only secondary tubers, leaving the main root intact; cultivate commercially; regulate wild harvesting.

What is the scientific name, medicinal use, and sustainable measure for Rooibos?

Scientific name: Aspalathus linearis. Uses: caffeine-free antioxidant tea used to relieve allergies, digestive problems, and mild skin irritations. Sustainable measure: harvest by cutting stems instead of uprooting plants, replant after harvesting, and conserve fynbos habitat.