Biological Impacts of Climate Change Notes

Climate Change

• In the last 100 years, Earth’s mean temperature rose by 0.6°C, a rate not seen in 10,000 years. This rapid increase is alarming and has significant implications for ecosystems and human societies.

• The major cause is anthropogenically produced greenhouse gases, with other synergistic factors involved. These gases trap heat in the atmosphere, leading to a warming effect. The primary sources of these gases are the burning of fossil fuels, deforestation, and industrial processes.

• Conservation concerns: Heavy consequences expected within the next 50 years. These consequences include rising sea levels, more frequent and intense heatwaves, changes in precipitation patterns, and disruptions to ecosystems.

• Climate change will likely become the biggest threat to biodiversity due to unmatched scale, duration, severity, and synergy with other threats. Many species may not be able to adapt quickly enough to survive.

The Nature of Climate Change

• Climate shifts are generally caused by changes in the retention and distribution of solar energy across the planet. Factors such as changes in Earth's orbit, variations in solar activity, and volcanic eruptions can all influence the amount of solar energy that reaches the Earth's surface.

• Solar radiation passes through the atmosphere as short wavelength ultraviolet (UV) waves.

Greenhouse Effect

• Important greenhouse gases are CO2, CH4, and H_2O, which block radiation in the infrared spectrum (long wave). These gases absorb and re-emit infrared radiation, trapping heat in the atmosphere.

• Greenhouse gases keep the Earth's surface approximately 60°F warmer than it would be without them. This natural greenhouse effect is essential for maintaining a habitable temperature on Earth.

• Life as we know it depends on the greenhouse effect. Without it, the Earth would be too cold to support liquid water and most known life forms.

Climate Change through Time

• Since the industrial revolution, burning fossil fuels has increased greenhouse gases by about 40\%. This increase is primarily due to the combustion of coal, oil, and natural gas for energy production, transportation, and industrial processes.

• Short-term variation is not climate change. Climate change refers to long-term trends and patterns in temperature, precipitation, and other climate variables.

• Climate vs. weather.

• Small bubbles trapped in polar glaciers yield information on atmospheric composition, including CO2 concentrations and ratios of {}^{18}O2 to {}^{16}O_2, which accurately reflect past temperatures. Scientists analyze these air bubbles to reconstruct past climate conditions.

• This technique has yielded an accurate temperature history going back 740,000 years. This long-term record provides valuable insights into natural climate variability and the impact of human activities on the climate system.

• Relationship between temperature and CO2 over the past 160,000 years. There is a strong correlation between atmospheric CO2 concentrations and global temperatures, with higher CO_2 levels corresponding to warmer temperatures.

• Cretaceous period: High carbon (CO2) sequestration due to high plant productivity and low decomposition rates. During this period, warm and humid conditions promoted the growth of lush vegetation, which absorbed large amounts of CO2 from the atmosphere.

• Tertiary period: High carbon sequestration due to woody plants explosion and formation of limestone deposits. The expansion of forests and the formation of limestone rocks contributed to the removal of CO_2 from the atmosphere.

Human Enhancement of Greenhouse Effect

• CO_2 has risen 46\% since 1910, which is well outside historical ranges based on ice-core data and instrument data. This rapid increase is primarily due to human activities, such as burning fossil fuels, deforestation, and industrial processes.

• Human activities are altering the global Carbon cycle, consequently affecting other biogeochemical cycles like the water and nitrogen cycles. These alterations have far-reaching consequences for ecosystems and human societies.

Current and Future Climate Change

• Global climate models (GCMs) are based on processes by which atmospheric greenhouse gases affect global climate. These models use complex mathematical equations to simulate the interactions between the atmosphere, oceans, land surface, and ice.

• All models indicate warming should be greatest at the poles and least in the tropics. This is due to factors such as the albedo effect (ice and snow reflect more sunlight) and changes in ocean currents.

• Example: In some parts of Alaska, Canada, and Siberia, the mean annual temperature has risen 2-4°C since 1900. This warming has led to thawing permafrost, melting glaciers, and changes in vegetation patterns.

• Some expected/observed trends:

  • Fewer nights below freezing in the mid-latitudes.

  • Changes in precipitation (especially in intensity). Some regions are experiencing more frequent and intense droughts, while others are experiencing more frequent and intense floods.

  • More frequent and severe meteorological events. These events include heatwaves, hurricanes, and wildfires.

• Trends vary regionally. The impacts of climate change are not uniform across the globe, with some regions experiencing greater warming or more significant changes in precipitation than others.

• Observed temperature trends over the last 100 years show warming in black and cooling in gray, with size indicating magnitude of change.

• Observed precipitation trends over the last 100 years show wetter conditions in black and drier conditions in gray, with size indicating the magnitude of change.

• GCMs predict a continued global increase in precipitation (with big changes in distribution).

Oceans: Sea Level and Circulation

• 20,000 years ago, sea levels were as much as 120m lower than current levels. This was due to the large amount of water stored in ice sheets during the last glacial period.

• Annual changes were relatively small (e.g., 0.1-0.2mm) over the past 3,000 years. Sea levels have been relatively stable for the past few thousand years.

• However, the past 200 years have seen a rapid rise in ocean levels (1-2mm/year) due to:

  • Melting polar ice caps (0.2-0.4mm/year). The melting of glaciers and ice sheets is contributing to sea level rise.

  • Thermal expansion (1mm/year). As the ocean warms, the water expands, causing sea level to rise.

• Observed sea levels rise over 300 years in 3 European cities.

• Major ocean circulation systems are being affected by the rise in atmospheric temperatures. Changes in ocean temperatures and salinity are disrupting ocean currents.

• El Niño events have increased in frequency and intensity (warming of mid-Pacific, pushing away cold waters). These events can have significant impacts on weather patterns around the world.

Snow, Ice, and Hydrological Changes

• Widespread retreat of glaciers in North & South America, New Zealand, Africa, Europe, and Asia.

  • Example: Glacier National Park (GNP) has lost 77% of its glaciers and they're expected to be gone by 2030.

  • Example: Mt. Kilimanjaro has lost 70% of its glaciers and they're expected to be gone by 2040.

  • Glacier retreat (Columbia Glacier).

• Reduced Salinity of North Atlantic Waters. The melting of ice sheets and glaciers is adding freshwater to the ocean, reducing salinity.

Predicted Biological Impacts

• Many biological processes are tied to climatic events, so climate change will have profound impacts. Changes in temperature, precipitation, and other climate variables can disrupt ecosystems and affect the distribution and abundance of species.

• Climate determines the type of biome. Different biomes, such as forests, grasslands, and deserts, are characterized by distinct climate conditions and vegetation types.

• One approach to predict species’ responses is to identify its “climate envelope” from climate and distribution information. This involves determining the range of climate conditions in which a species can survive and reproduce.

• A simplistic expectation of biotic responses is that species may alter their distribution quickly (e.g., birds) or gradually (e.g., plants - seed dispersal). Some species may be able to shift their ranges to track suitable climate conditions, while others may be unable to adapt or move quickly enough.

• Paleoecologists have found species that used to co-occur are no longer found together due to specific habitat requirements other than climate. Climate change can disrupt ecological relationships and lead to changes in community composition.

• Observed elevation shifts in temperature, precipitation, and conifers in 80 years (Sierra Nevada, CA).

• Vegetation-climate mismatch. In some cases, vegetation may not be able to keep pace with climate change, leading to mismatches between the distribution of plants and the climate conditions they experience.

Extreme Weather

• Many ecosystems are strongly influenced by weather extremes.

  • Example: Frost boundaries and tropical plants. Frost can limit the distribution of tropical plants.

  • Example: Precipitation limits and animals & plants; desertification progression. Water availability is a key factor that limits the distribution of plants and animals, and drought can lead to desertification.

• Single events can have long-term effects.

  • Example: Drought and Darwin’s finches. During the 1976 drought, average beak depth was 9mm, while after the dryer conditions of 1978, the average beak depth was 10mm.

• Prolonged climate swings impact many reptiles.

  • Example: Map turtles, where males are produced at temperatures <28°C and females at >30°C.

• Many insect populations boom/bust with climatic events.

• Host-parasite and infectious diseases are strongly influenced by climatic events. Climate change can alter the distribution and transmission of diseases.

• Even if extremes don’t change, their frequency will change.

• An increase in both mean and variance temperatures, leading to more record high temperatures.

Community Changes

• A reasonable expectation is new community types (as a result of changes in abundances, species relocations, extinctions). Climate change can lead to the formation of novel communities with unique species assemblages.

• Some ecosystems may disappear, and new ones may arise (novel ecosystems).

Observed Biological Impacts

• So far, impacts are relatively reduced compared to other threats to biodiversity but are expected to become overwhelming within this century.

• Studies examining impacts of climate change on ecosystems are currently correlative and inferential rather than experimental.

  • Example: impacts on ecosystem function and structure.

  • Proposed UTRGV-UAT project: “Potential effects of global warming in gulf coast: the case of black mangrove along a latitudinal gradient”

Evolutionary & Morphological Changes

• Rapid responses concerning evolutionary adaptations are possible.

  • Example: Drosophila subobscura from Europe changed wing length after 20 years in the US.

  • Example: NM desert rats have 16% smaller body size with warming over 8 years.

• Reason is not clear, but change consistent with climate.

Phenological Shifts

• Phenological Shifts in organisms (ex. arrival of migratory birds)

• Many biological events are temperature-driven (e.g., leaf emergence, hatching).

  • Example: In Arizona, Mexican Jays now hatch 10 days earlier.

  • Growing seasons extended.

  • Many other examples (migratory species).

• There can be desynchronization. Climate change can disrupt the timing of biological events, leading to mismatches between species and their resources.

Changes in Abundance and Community Reassembly

• Community structure has been changing (in temperate climates).

  • Warm-adapted species are flourishing, and cold-adapted species are declining.

• Example: community structure (fish) vs. water temperature in California. As water temperature increases, there is a shift in Fish species proportion. There were less northern species, and more southern species.

• Example: woody encroachment into grasslands (coastal prairies, moist savannas)- another example of community structure changes

  *Increases in temp, H2O, and CO_2, result in increases in woody species coverage (C3 vs C4)

Range Shifts

• Many examples of range shifts in apparent direct response to climate change.

  • Montane studies have shown plants and animals are being found at higher elevations (e.g., conifers in Sierra Nevada but mismatch; red and arctic fox in Canada).

  • In North America and Europe, 2/3 of butterflies (58 species) studied have shifted North by 100 km per decade.

• Patterns of population extinctions of Edith’s checkerspot butterfly from 1860 to 1996. Significantly higher extinctions in the South.

Impacts of sea level rise

• Contractions in distribution range of coastal species due to:

  • Soil salinity increases.

  • Flooding regime changes.

  • Soil carbon fluxes and biochemistry changes.

Direct effects of CO_2 enrichment

• Differential plant photosynthetic responses favor C3 over C4 and CAM plants.

• Limiting nitrogen.

• Ocean acidification. The absorption of CO_2 by the ocean is leading to a decrease in pH, which can have negative impacts on marine organisms.

• Plant acclimation (metabolic and morphologic) with an uncertain long-term outcome.

Changes in ecosystem process

• NPP is increasing due to extended growing season. In some regions, the growing season has been extended due to warmer temperatures, leading to increased plant growth.

• Boreal biomes are shifting from carbon sinks to carbon sources due to increased decomposition and fire frequency. Warmer temperatures are increasing decomposition rates in boreal forests, releasing carbon into the atmosphere. Increased fire frequency is also contributing to carbon emissions.

• Compensation with increased growth is uncertain due to water stress, pests, and fires affecting growth rates.

Conservation Implications of Climate Change

*Extinctions

• There has been a spike in extinctions in recent centuries (6th mass extinction).

• However, very few extinctions are directly attributable to Climate Change so far.

  • ex. 2 tropical frogs Bramble Cay Melomys (Melomys rubicola) has now been declared Extinct, and will go down in history as the first mammal known to have been wiped out by human-induced climate change. This humble species was known only from a small island (of only five hectares) in the Great Barrier Reef, and the opportunity to prevent its extinction was missed, as the recommended conservation action to develop a captive breeding and reintroduction program was not actioned. It is likely that its decline occurred due directly to storm surges across the entire island (killing individuals) and/or due to ongoing and episodic reduction in vegetation (probably also due to storm surge). Photo © Ian Bell ex. 1 endemic rodent

• Climate Change affects species differently, thus species distributions and abundances change, and therefore communities change.

• Many already endangered species have limited dispersal, small ranges, and strong local adaptations, leading to higher risk due to Climate Change.

Responses to Climate Change by Managers

• Most managers and conservation planners focus on local-scale projects, but regional or global considerations are more important than ever due to climate change.

• Adaptive approaches managers could use:

  • Susceptibility analysis of the impact of Climate Change.

  • Design/adjust reserves to allow movement. Protected areas can be designed to allow species to move to more suitable habitats as the climate changes.

  • Promote corridors. Corridors can connect isolated populations and allow species to move between habitats.

  • Implement dynamic habitat conservation plans (adaptive management). Conservation plans should be flexible and adaptable to changing conditions.

  • Alleviate non-climate stressors. Reducing other threats, such as habitat loss and pollution, can help species cope with climate change.

  • Use of climate envelope models and regional-scale climate models to identify escape zones and assurance wild populations.

Other impacts

• A warming planet also leads to extreme weather, both cold and hot. Climate change is increasing the frequency and intensity of extreme weather events.

• A 2017 study found that the frequency of polar-vortex events has increased by as much as 140% over the past four decades.

• Photosynthesis and transpiration relationships influenced. Climate change can affect the balance between photosynthesis and transpiration in plants, which can have impacts on plant growth and survival.