Chapter 25- Global Ecology

What is a 'pool' or 'reservoir' in a biogeochemical cycle?

The amount of an element stored in a component of the biosphere.

What is a 'flux' in a biogeochemical cycle?

The rate of movement of an element between pools.

What are the four major global carbon pools?

Atmosphere, oceans, land surface (vegetation and soil), and sediments/rock.

Which carbon pool is the largest and most stable?

Sediments and rocks, containing 99% of global carbon.

What are the largest fluxes in the global carbon cycle?

Gross primary production (GPP) and respiration.

Why is the deep ocean a large carbon reservoir?

Due to fluxes like sinking detritus and shells, and limited mixing with surface waters.

How does CO₂ acidify oceans?

CO₂ forms carbonic acid in water, releasing H⁺ ions and lowering pH.

What are the two main anthropogenic sources of atmospheric CO₂?

Deforestation and fossil fuel combustion.

What is the current contribution of fossil fuels to anthropogenic CO₂ emissions?

About 92% as of 2018.

What is a FACE experiment?

Free-Air CO₂ Enrichment: CO₂ is injected into forest plots to simulate elevated CO₂ levels.

What did DeLucia et al. (1999) discover in the loblolly pine FACE experiment?

Elevated CO₂ increased NPP by 25%, enhancing carbon input.

What effect does ocean acidification have on marine organisms?

It dissolves calcium carbonate shells and reduces shell formation.

What trend is shown in Figure 25.5?

Coral calcification rates declined 14% between 1990–2009 due to acidification.

Coral calcification rates declined 14% between 1990–2009 due to acidification.

They varied with glacial cycles, reaching 408 ppm in 2019.

Why is CH₄ a powerful greenhouse gas?

It is 25 times more effective than CO₂ per molecule.

What are some anthropogenic sources of methane?

Livestock, rice paddies, fossil fuel use, and biomass burning.

What is the largest nitrogen pool?

Atmospheric N₂, biologically unavailable to most organisms.

What are 'reactive' nitrogen compounds?

Active forms like ammonia and nitrate usable by organisms.

What process adds reactive nitrogen to the biosphere naturally?

Nitrogen fixation by bacteria.

What are the three major human processes altering the N cycle?

Haber–Bosch process, N-fixing crops, fossil fuel combustion.

What are some consequences of increased reactive N?

Acid precipitation, eutrophication, biodiversity loss, pollution.

What is the primary source of biologically available phosphorus?

Weathering of rock and mineral decomposition.

How does most phosphorus move from land to oceans?

Through erosion and particulate organic matter.

What are major human impacts on the phosphorus cycle?

Mining, fertilizer use, erosion, and wastewater discharge.

What are the major pools of sulfur?

Rocks, marine sediments, and ocean water as sulfate.

How is sulfur naturally emitted into the atmosphere?

Volcanoes, sea spray, and microbial activity.

What are the major human sources of sulfur emissions?

Burning coal/oil and metal smelting.

How does acid precipitation form from sulfur and nitrogen compounds?

They oxidize into sulfuric and nitric acids, forming acid rain.

What are the effects of acid precipitation on soil?

Loss of cations (Ca²⁺, Mg²⁺, K⁺) and reduced soil fertility.

What is climate change?

A directional change in climate over at least three decades.

What causes Earth's warming?

Anthropogenic emissions of greenhouse gases, especially CO₂, CH₄, and N₂O.

Which greenhouse gas contributes most to warming?

CO₂, followed by CH₄ and N₂O.

What is the greenhouse effect?

Warming caused by the atmosphere absorbing and reradiating infrared radiation from Earth's surface.

What does the IPCC say about the cause of recent climate change?

It is extremely likely (95%-100%) that human influence is the dominant cause.

What is the Anthropocene epoch?

A proposed new geologic era defined by the global impact of human activities, including climate change.

What does Figure 25.11 show?

A: Temperature anomalies since 1880; B: regional warming trends; C: precipitation changes.

What does Figure 25.12 show?

A: Trends in CO₂, CH₄, and N₂O; B: CO₂ is the dominant contributor to radiative forcing.

What does Figure 25.13 demonstrate?

Observed warming is best explained when both natural and anthropogenic factors are included in models.

What biological effects have been observed due to warming?

Earlier bird migration, coral bleaching, species range shifts, local extinctions.

How have Alpine plant communities changed?

Species richness increased at mountain summits due to upward movement (Fig. 25.14).

What did Parmesan et al. (1999) find in butterflies?

63% of European species shifted northward.

What did Sinervo et al. (2010) find in lizard populations?

12% of Mexican populations went extinct due to limited foraging time from spring heat.

What did Nemani et al. (2003) find about global NPP?

It increased 6% from 1982–1999 (Fig. 25.15), but declined later due to drought.

What are effects of Arctic warming on CO₂?

Tundra switched from sink to source; soil C loss exceeds gains from NPP.

What elevational change corresponds to 2.9°C warming?

What is a 'no-analog' community?

A community with a species composition not found in modern ecosystems, often due to unique climates (Fig. 25.16).

Why might plants not track climate change?

Dispersal rates are too slow—5–10 km/year needed; barriers like habitat fragmentation exist.

What extinction risk does Urban (2015) project?

Up to 17% of Earth's species could be lost due to climate change.

How is forest composition affected?

Increased beetle outbreaks and fire frequency due to warming and longer frost-free seasons.

How can climate change affect nutrient cycling?

How can climate change affect nutrient cycling?

What is acid deposition?

Deposition of sulfuric and nitric acids from the atmosphere via rain (wet) or particles (dry).

What causes acid precipitation?

Oxidation of sulfur and nitrogen compounds forming H₂SO₄ and HNO₃.

What is nitrogen deposition?

Deposition of reactive nitrogen (NH₄⁺, NO₃⁻) from fossil fuel burning and agriculture.

What does Figure 25.17 show?

Air quality monitoring in Sierra National Forest, highlighting pollution effects even in 'pristine' areas.

What does Figure 25.18 show?

High tree mortality in European forests linked to acid precipitation and nutrient loss.

What does Figure 25.19 demonstrate?

Decrease in acidity of precipitation in the U.S. between 1990 and 2017.

What does Figure 25.20 show?

Increases in global nitrogen deposition from 1860 to projected levels in 2050.

What does Figure 25.21 show?

Model by Aber et al. on how nitrogen saturation impacts forests via soil nutrient loss.

What does Figure 25.22 show?

Nitrogen deposition reduces species richness in UK grasslands; N explained 55% of the variation.

How does acid precipitation affect soil chemistry?

H⁺ replaces base cations (Ca²⁺, Mg²⁺, K⁺), leading to leaching and acidification.

What is acid neutralizing capacity?

The ability of soil or water to resist changes in pH, often via base cations.

Why is aluminum release harmful?

Al³⁺ is toxic to roots, invertebrates, and fish; released under acidic conditions.

What is nitrogen saturation?

What is nitrogen saturation?

What are the ecological effects of nitrogen saturation?

N loss, release of N₂O (greenhouse gas), leaching of Ca²⁺ and Mg²⁺, and soil acidification.

How does nitrogen deposition impact biodiversity?

Reduces species richness, favors fast-growing or invasive species, harms rare natives.

What are 'dead zones' and what causes them?

Low oxygen marine zones caused by eutrophication from nitrogen runoff.

How can reactive nitrogen impact groundwater?

NO₃⁻ leaching can contaminate water and cause conditions like blue baby syndrome.

What did Stevens et al. (2004) find in the UK?

Higher N deposition significantly lowered plant species richness across 68 grassland sites.

What did Simkin et al. (2016) observe in the U.S.?

25% of surveyed sites showed biodiversity loss linked to nitrogen deposition.

What happened in the Netherlands due to nitrogen?

Species-rich heathlands were replaced by species-poor grasslands.

What is the role of stratospheric ozone?

It protects Earth from harmful ultraviolet-B (UVB) radiation.

Why is tropospheric ozone harmful?

It is a strong oxidant that damages respiratory systems, plants, and acts as a greenhouse gas.

What caused the Antarctic ozone hole?

CFCs and other chlorinated compounds releasing reactive chlorine atoms that destroy ozone.

What does UVB radiation do to living organisms?

Damages DNA, impairs immune systems, and increases cancer risk.

What is the difference between stratospheric and tropospheric ozone?

Stratospheric ozone protects life; tropospheric ozone harms organisms and ecosystems.

What does Figure 25.23 show?

Dramatic springtime ozone depletion over Antarctica from 1979 to 2019.

What does Figure 25.24 show?

Declines in ozone-depleting substances since the Montreal Protocol.

How has UVB radiation changed since ozone depletion?

It increased by up to 130% in Antarctica and 22% at mid-latitudes.

Why is skin cancer incidence rising in some regions?

Increased UVB exposure due to ozone loss, especially affecting fair-skinned populations in high-UV areas.

What are the ecological effects of UVB increase?

Species differ in UVB sensitivity, leading to altered community composition.

What historical adaptation did UVB drive in humans?

Selection for melanin production in high-UV environments to prevent DNA damage.

What is the Montreal Protocol?

An international agreement to reduce CFC production and emissions.

What success has followed the Montreal Protocol?

CFC levels have declined and ozone layer recovery is underway, expected by 2050.

What produces tropospheric ozone?

Sunlight-driven reactions involving NOₓ, CO, CH₄, and VOCs.

What are the health effects of tropospheric ozone?

Respiratory damage, eye irritation, and increased childhood asthma.

What are the ecological effects of tropospheric ozone?

Reduces plant photosynthesis and growth; lowers forest productivity by ~10%.

How has tropospheric ozone changed in developed countries?

Decreased near urban areas due to emission controls on VOCs and NOₓ.

What about in developing countries?

Still rising due to less regulation, with severe pollution in cities in China and India.