Conservation Biology and Global Change

Fragmentation and Habitat Edges

• Definition of Edges: The boundaries, or edges, between ecosystems are defining features of landscapes. These areas represent a transition between different environmental conditions.

• Physical Characteristics: An edge has its own unique set of physical conditions, which differ significantly from those on either side of it (the interior of the adjacent ecosystems).

• Species Interactions: Some species take advantage of edge communities, utilizing them to access resources from both adjacent areas simultaneously.

• Fragmentation: Human activity often causes habitat fragmentation, creating more edges and smaller, isolated patches of habitat.

Movement Corridors and Connectivity

• Definition: A movement corridor is a narrow strip or a series of small clumps of habitat that connect otherwise isolated habitat patches.

• Benefits of Corridors:

  • Dispersal: They promote the movement of individuals between populations.

  • Genetic Health: By facilitating movement, they reduce the risk of inbreeding within isolated populations.

• Artificial Corridors: In regions with heavy human usage, artificial corridors (such as wildlife overpasses or underpasses) are sometimes constructed to bridge gaps created by infrastructure.

• Risks of Corridors: Corridors can be harmful by facilitating the spread of disease-carrying organisms or invasive species between previously separated populations.

Establishing Protected Areas

• Global Status: Governments worldwide have set aside approximately $7\%$ of the Earth's land in various forms of reserves.

• Design Challenges: The placement and design of reserves pose significant challenges for conservationists:

  • Management Goals: There is an ongoing debate about whether reserves should be actively managed to protect specific threatened species or left in a strictly natural, unmanaged state.

• Disturbance Theory: Modern philosophy regarding nature reserves dictates that disturbances (like fire or flood) must be considered a functional and necessary component of all ecosystems.

Biodiversity Hot Spots

• Definition: A biodiversity hot spot is a relatively small geographic area characterized by:

  • A high concentration of endemic species (species found nowhere else in the world).

  • A large number of endangered and threatened species.

• Distribution: Hot spots are found globally, with significant concentrations near the equator in both terrestrial and marine environments.

• Challenges and Biases in Hot Spot Designation:

  • Taxonomic Bias: An area that is a hot spot for one group (e.g., birds) may not be a hot spot for another (e.g., fungi).

  • Categorical Bias: Designations are often biased toward saving vertebrates and vascular plants.

  • Scope: Focusing only on hot spots emphasizes a very small fraction of the Earth's surface.

  • Stability: The environmental conditions favoring a specific hot spot community may change over time due to climate shifts.

Reserve Design and Zoned Reserves

• The Scale Debate (SLOSS): Conservationists debate which is better: fewer large reserves or more numerous small reserves.

  • Large Reserves: Support large, far-ranging animals with low-density populations and species sensitive to habitat edges.

  • Small Reserves: May be easier to acquire and can slow the spread of disease between populations by maintaining isolation.

• Zoned Reserves: These systems include relatively undisturbed areas (core zones) surrounded by modified areas where human activities are regulated to avoid harming the protected core.

  • Buffer Zones: The modified areas surrounding the core that serve as a protective transition.

  • Costa Rica Case Study: Costa Rica is a global leader in establishing zoned reserves, with a network of protected land and ocean areas that support conservation and eco-tourism.

Urban Ecology

• Definition: The field of urban ecology examines the interactions between organisms and their environment specifically within urban settings.

• Urban Streams: A critical research area focuses on urban streams, which characteristically experience rapid water level fluctuations following rainfall (flashiness).

• Restoration Success: The restoration of Guichon Creek, located near Vancouver, British Columbia, has successfully allowed for the reestablishment of cutthroat trout.

Nutrient Enrichment and Human Impact

• Nutrient Displacement: Human activity often removes nutrients from one part of the biosphere and adds them to another.

  • Agricultural Export: Harvesting crops removes nutrients from the local agricultural ecosystem that would otherwise return to the soil via decomposition.

  • Soil Depletion: Continuous agriculture leads to the depletion of natural soil nutrients.

  • Fertilizers: To compensate for depletion, humans add nitrogen and other synthetic nutrients, which can then leach into surrounding environments.

Toxins and Biological Magnification

• Synthetic Toxins: Humans release many toxic chemicals, including synthetics that do not exist naturally and for which microorganisms have no degradation pathways.

• Persistence: Many harmful substances persist for long periods in the environment.

• Biological Magnification: This process involves the concentration of toxins at higher trophic levels, where biomass is lower. Toxins accumulate in tissues and become increasingly concentrated in predators.

• Case Studies in Magnification:

  • PCBs (Polychlorinated Biphenyls): In the Great Lakes, Herring gull eggs contain PCB levels $5,000$ times greater than the levels found in phytoplankton.

  • Concentration Gradient Example:

    • Phytoplankton: $0.025\,ppm$

    • Zooplankton: $0.123\,ppm$

    • Smelt: $1.04\,ppm$

    • Lake trout: $4.83\,ppm$

    • Herring gull eggs: $124\,ppm$

  • DDT: Rachel Carson’s 1962 book Silent Spring brought attention to the biomagnification of DDT in birds. Following a ban in the United States in 1971, bird populations recovered.

  • Malaria Trade-off: Some countries still face a dilemma between using DDT to control malaria-carrying mosquitoes and the environmental risks to other species.

• Pharmaceuticals: Sex steroids (like estrogen from birth control) enter freshwater through sewage and runoff; these can shift the sex ratio of fish populations toward females.

Greenhouse Gases and Climate Change

• The Greenhouse Effect: $CO_2$, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth. This is essential for keeping the Earth’s surface at habitable temperatures, but excess gases cause overheating.

• Rising $CO_2$ levels: Atmospheric $CO_2$ concentration has increased steadily due to the burning of fossil fuels.

• Temperature Statistics:

  • Average global temperature has increased by $0.9\,^\circ C$ since 1900.

  • A further rise of at least $3\,^\circ C$ is predicted by the end of the 21st century.

Biological Effects of Climate Change

• Cellular Level:

  • Increased temperatures affect enzymatic reaction rates and impair cellular defenses.

  • Pine Trees: Drought-stressed trees produce less resin (produced by resin cells), making them vulnerable to pine beetles. Warmer temperatures have also shortened the maturation and reproduction time for these beetles, leading to massive forest destruction.

• Individual Organism Level:

  • Overheating risks lead to reduced food intake and reproductive failure.

  • American Pikas: These animals must spend more time in burrows to escape heat and less time foraging. Extinctions are most common at sites with high summer temperatures (observed between $8\,^\circ C$ and $16\,^\circ C$) and small habitat areas.

• Population Level:

  • Climate change alters the timing of growth, reproduction, and migration.

  • Caribou and Alpine Chickweed: Caribou migrate north to eat sprouting Alpine chickweed. Earlier spring plant growth (mismatch in timing) has led to food shortages and a fourfold ($4\times$) drop in caribou offspring production.

Sustainable Development and Future Outlook

• Mitigation of Climate Change: Strategies include reducing energy use, converting to renewable sources, reducing deforestation, and stabilizing $CO_2$ emissions through international cooperation.

• Sustainable Development: Defined as development that meets the needs of the present without limiting the ability of future generations to meet their own needs.

• Sustainable Biosphere Initiative: A program aimed at acquiring the ecological information necessary for the responsible management and conservation of Earth’s resources.

• Interdisciplinary Nature: Sustainable development requires integration between life sciences, social sciences, economics, and humanities.

• Biophilia: A concept reflecting a human ancestral attachment to nature and the diversity of life, which continues to guide the field of biology today.