Global Ecology - Climate Change Notes

Introduction

• Humans are increasingly changing the environment on a global scale.

• Atmospheric emissions of pollutants, dust, and greenhouse gases have caused widespread environmental problems.

Focus of Global Ecology

• A major focus is the study of the environmental effects of human activities.

• Understanding global biogeochemical cycles is crucial.

  • Biogeochemistry: Study of the physical, chemical, and biological factors that influence movement and transformation of elements.

Global Biogeochemical Cycles

• Four important elements:

  • Carbon: Chemical backbone of life.

  • Nitrogen: Amino acids, protein.

  • Phosphorous: Tissues, cell repair, genetic material (RNA, DNA).

  • Sulfur: Amino acids, enzymes.

• Importance:

  • Essential to biological activity.

  • Can act as pollutants in the global environment.

• Carbon:

  • Critical for biological activity.

  • Role in energy transfer (ATP) and construction of biomass.

  • Backbone & versatility of carbon is indispensable for life.

  • Carbon has the ability to combine with many other elements to form a wide variety of molecules, each specialized for the functions it carries out in the cell.

Nitrogen

• Nitrous oxide (N2O).

• Molecular N (N2) - most abundant uncombined element in the air.

  • Inert.

• Plants:

  • Chlorophyll.

  • Protein amino acids, proteins and even our DNA.

Global Carbon Cycle

• At a global scale, carbon moves between atmospheric, terrestrial, and oceanic pools over weeks to decades.

• Changes in the global carbon cycle are influencing Earth’s climate.

• Gt (Gigatons): A billion metric tons.

Pools and Fluxes

• Pool (or reservoir): The amount of an element in a component of the biosphere.

• Flux: Rate of movement of an element between pools.

  • Example: Terrestrial plants are a pool of carbon; photosynthesis represents a flux.

Carbon Cycle Diagram

• Pool or reservoir: Boxes represent major pools of C, measured in petagrams (Pg).

  • $1 \text{ Pg} = 2,204,622,621,849 \text{ pounds}$

• Fluxes: Arrows represent fluxes per year.

• Key pools:

  • Atmosphere: 760 Gt

  • Surface ocean waters: 920 Gt

  • Vegetation: 650 Gt

  • Soils: 1,500 Gt

  • Marine biota: 3 Gt

  • Deep ocean waters: 38,000 Gt

  • Rocks: $60 \times 10^6$ Gt

  • Benthic sediments: 150 Gt

• Key fluxes:

  • Atmosphere-ocean flux: 91 Gt (in), 92 Gt (out)

  • GPP (Gross Primary Production): 123 Gt

  • Respiration: 120 Gt

  • Fossil fuels: 10.6 Gt

  • Land use change: 0.9 Gt

  • Transport in rivers: 0.8 Gt

  • Detritus: 39 Gt

Major Pools of Carbon

• Atmosphere, oceans, land surface (soils and vegetation), sediments, and rock.

• 99% of global C is in sediments and rock, the most stable pool.

  • Fluxes occur on geological time scales.

Carbon Exchange

• Ocean surface water takes up $CO_2$ from the atmosphere by diffusion (high concentration to low concentration).

• Carbon is transferred to deeper water mostly as organic detritus and carbonate shells.

• Upwellings bring C-rich water to the surface, releasing $CO_2$ to the atmosphere.

• Surface level: 75-200 m (most biological activity).

• Deeper colder water plays a significant role.

Terrestrial Pool

• Soils contain twice as much C as plants.

• $CO_2$ is exchanged with the atmosphere mostly by photosynthesis and respiration.

• Prior to the Industrial Revolution, these two fluxes (terrestrial and atmospheric) were roughly equal, with no net change in atmospheric $CO_2$.

Atmospheric Carbon

• Carbon in the atmosphere occurs primarily as carbon dioxide ($CO<em>2$) and methane ($CH</em>4$).

• Both are greenhouse gases.

• Greenhouse gases influence atmospheric absorption of infrared radiation and reradiation from Earth’s surface.

Anthropogenic Release of Carbon

• Anthropogenic release of C to the atmosphere from the terrestrial pool results from land-use change, mostly deforestation (cutting and burning), and the burning of fossil fuels.

• Before the mid-nineteenth century, deforestation was the main anthropogenic flux.

Anthropogenic Emissions

• Anthropogenic emissions of $CO_2$ almost tripled from 1970 to 2018.

• About half is taken up by the oceans and terrestrial biota.

• This proportion will decrease because terrestrial and ocean uptake will not keep pace with the rate of atmospheric increase.

Methane

• Emissions of $CH_4$ have also increased, from fossil fuel use, agriculture (mostly rice), livestock, and burning forests and crops.

• $CH_4$ is emitted naturally by anaerobic methanogenic bacteria in wetlands and rumens of ruminant animals.

• $CH<em>4$ is 25 times more effective as a greenhouse gas than $CO</em>2$.

• Methane’s average lifespan in the atmosphere is about 10-12 years (oxidation).

Climate Change

• Climate change: Directional change in climate over a period of at least three decades.

• Earth is currently experiencing significant climate change (IPCC 2013).

• Average global surface temperature increased 0.97^"">\degree C between 1880 and 2018.

Disturbances and Mortality

• Disturbances add significant mortality within populations.

• Example: Australian bush fires.

  • Human-induced climate change increased the risk of the weather conditions that drove the fires by at least 30%.

• Critical in determining species geographic ranges.

• Loss of sea ice affects polar bears’ ability to find food.

Effect of Warming

• Infected with the bacteria Pasteurella multocida, which is normally harmless, but when exposed to unusually warm and wet weather, it became deadly, leading to blood poisoning.

• Example: 220,000 saiga antelope died suddenly in Kazakhstan (60% of population).

Effects Associated with Warming

• Widespread retreat of mountain glaciers.

• Thinning of the polar ice caps.

• Melting permafrost.

• Rate of sea level rise greater than any in the past 3,000 years.

Ecological Responses

• Organisms have already begun to respond to climate change.

  • Earlier bird migrations.

  • Local extinction of amphibian and reptile populations.

  • Earlier leaf-out of vegetation.

Geographic Ranges

• Plant and animal species are now shifting to higher elevations at an average rate of 36.1 feet (11.0 meters) per decade, and they’re moving to higher latitudes at about 10.5 miles (16.9 kilometers) per decade.

Butterfly Ranges

• Parmesan and Yohe (2003) found that 63% of European butterfly species have shifted ranges northward; only 3% shifted southward.

Lizard Extinctions

• Extinction of lizard populations in Mexico was linked to warmer spring temperatures, which limited foraging time during the breeding season (Sinervo et al. 2010).

• Using models of lizard physiology and projections for climate warming, they predict 39% of lizard populations will go extinct by 2050.

Migratory Animals

• Migratory animals may be affected.

  • Fish and whales may have to make longer journeys to find prey (new feeding behaviors and migration patterns).

  • Birds arrive earlier in spring, but plants and invertebrates they depend on for food may not be available at the same time (Mismatch).

Forest Composition

• Climate change is impacting forest composition in western North America.

• Mountain bark beetles now complete two life cycles per year and are found at higher elevations and latitudes.

• Forest fires have doubled since 1984, due to warmer weather and lower moisture content of fuel.

Evolutionary Change and Dispersal

• Because climate change will be rapid, most plants and animals will not be able to respond with evolutionary change.

• Dispersal may be the only way to avoid extinction.

• Dispersal barriers and habitat fragmentation will be important constraints.

Habitat and Food Requirements

• For animals, habitat and food requirements are associated with specific vegetation types.

Cause for Optimism

• The world is taking the threat of climate change seriously.

• Aims to keep the rise in the global average temperature to ‘well below 2 degrees above pre-industrial levels.

Personal Lifestyle Actions

• Start with impactful actions.

• Lifestyles have a profound impact on our planet; our choices matter.

• Around two-thirds of global greenhouse gas emissions are linked to private households.

• Energy, food, and transport sectors each contribute about 20 percent of lifestyle emissions.

• Actions:

  • Save energy at home.

  • Walk, bike, or take public transport.

  • Eat more vegetables.

  • Consider your travel.

  • Throw away less food.

  • Reduce, reuse, repair, recycle.

  • Change your home's source of energy.

  • Switch to an electric vehicle.

  • Choose eco-friendly products.

  • Speak up.