Conservation Biology Lecture Notes Flashcards

Species and Landscape Approaches to Conservation

• Protecting a species often involves protecting its critical habitat, which can include breeding grounds, feeding areas, and migratory routes. The size and quality of the habitat are crucial determinants of species survival.

• International treaties (e.g., CITES) tend to be species-oriented, focusing on regulating trade and protecting endangered species from exploitation. These treaties play a key role in global conservation efforts.

• Conservation education often focuses on specific species (e.g., pandas, wolves) to raise public awareness and support for conservation. Flagship species serve as ambassadors for broader conservation goals.

• Much conservation biology research focuses on individual species, studying their ecology, behavior, and genetics to inform conservation strategies. This research provides essential data for effective management.

  • Populations are the units of evolution, and their genetic diversity is critical for adaptation to changing environments.

  • Maintaining evolutionary potential and ecological role is crucial for the long-term survival of species. Conservation efforts should aim to preserve genetic diversity and ecological function.

• Even larger views often focus on a few high-profile species (e.g., hotspots), attracting public interest and aiding conservation education. These species can galvanize support for protecting entire ecosystems.

• Flagship species examples: Morelet’s crocodile and neotropical otter. Using these species helps to protect the wetland environments they inhabit.

Population Conservation

• Populations are dynamic and change over time due to various factors such as birth rates, death rates, immigration, and emigration.

• Population changes are influenced by BIDE factors (Birth, Immigration, Death, Emigration). Understanding these factors is essential for effective population management.

• Other factors influence population dynamics, including resource availability, habitat quality, and interactions with other species.

• Sex ratios, age structure, and time of first reproduction influence population dynamics, collectively known as life history characteristics or traits. These traits play a crucial role in determining population growth rates.

• Modeling population change is relatively simple using mathematical models, but identifying the processes driving these changes is not. Determining the key drivers of population dynamics requires detailed ecological studies.

Mechanisms of Population Regulation

• Density-independent factors affect population size regardless of the density, such as natural disasters, climate change, and pollution.

• Density-dependent factors:

  • Per capita mortality increases or per capita birth decreases as population density increases due to factors like competition for resources.

  • Death or birth rate changes due to resource availability, impacting population growth and carrying capacity.

  • Death rate increases due to predation or parasitism, regulating population size and maintaining ecosystem balance.

  • Death or birth rate changes due to social interactions, such as territoriality and social hierarchies.

• Social behavior regulates access to resources:

  • Dominance behavior or aggression influences resource distribution and reproductive success within a population.

  • Exception: Higher densities needed for reproduction in colonial nesters, abalone, queen conch (avoiding Allee effect). These species benefit from group living and require a critical mass for successful reproduction.

• Example: No reproduction activity when density is less than 50/ha, illustrating the importance of population density for reproductive success.

Special Problems of Small Populations

• Four general causes of extinction:

  • Genetic losses (genetic drift) reduce genetic diversity and adaptive potential, making populations more vulnerable.

  • Demographic uncertainty (stochasticity) leads to unpredictable fluctuations in population size and structure.

  • Environmental uncertainty (stochasticity) results in variations in environmental conditions that affect survival and reproduction.

  • Catastrophes (natural or human-caused disasters, less predictable, large) can decimate small populations and lead to extinction.

• Genetic drift:

  • Changes in allele frequency leading to decreased genetic diversity and inbreeding depression, reducing the ability of the population to adapt to changing conditions.

• Demographic uncertainty:

  • Sex-ratio, reproductive success, and mortality rates can change quickly and randomly, making it difficult for small populations to recover from declines.

• Environmental uncertainty:

  • Can cause a sudden increase in reproductive failure or individual mortality, especially in populations that are already stressed.

• Catastrophes:

  • More irregular and larger scale than environmental uncertainty, causing widespread mortality and habitat destruction.

Source-Sink Concepts

• Source population:

  • Reproduction rate is greater than mortality rate, allowing the population to grow and disperse individuals to other areas.

  • Source habitat is of good quality, providing abundant resources and favorable conditions for survival and reproduction.

• Sink population:

  • Reproduction rate is lower than mortality rate; will go extinct without immigration from source populations.

  • Sink habitat is of marginal quality, with limited resources and unfavorable conditions for survival and reproduction.

• A metapopulation is frequently structured by source-sink dynamics, where not all populations are equally likely to go extinct. Source populations sustain sink populations through dispersal.

• The status of sources and sinks can vary between years. Environmental conditions and resource availability can change the quality of habitats.

  • In good years, even poor habitat may produce a surplus of individuals that can disperse to other areas.

• Identifying sources is important for conservation planning. Protecting source habitats is critical for maintaining metapopulation viability.

Metapopulations and Thresholds

• Rescue effect: Gene flow often maintains small populations by increasing genetic diversity and reducing the risk of extinction.

• Not all metapopulations have source-sink dynamics, just gene flow. Gene flow can occur even in the absence of source-sink dynamics, maintaining genetic connectivity among subpopulations.

• Minimum viable metapopulation size: The minimum number of subpopulations needed for metapopulation survival, ensuring long-term persistence.

• Some patchily distributed species may look like a metapopulation but have no gene flow, representing remnant populations. These populations are isolated and vulnerable to extinction.

  • These populations survive not because of immigration but due to local adaptation and resilience.

  • Example: Long-lived plants with asexual reproduction that can persist in isolated patches without the need for genetic exchange.

Modeling Approaches: Population Viability Analysis (PVA)

• PVA examines the demographic effect of different threats or management practices. It is a tool for assessing the long-term viability of populations.

  • Analysis of possible future population sizes (predict effects of threats and management). It helps in understanding the potential impacts of various factors on population dynamics.

  • A quantitative risk analysis (predict extinction risk). It provides a framework for evaluating the probability of extinction under different scenarios.

• Uses of PVA

• Data requirement:

  • Count-based PVA (= censuses) relies on population size estimates to project future trends.

  • Demographic or structured PVA (demographic data, matrices) incorporates age-specific survival and reproduction rates for a more detailed analysis.

  • Multi-site PVA (various subpopulations) accounts for spatial structure and connectivity among subpopulations.

• Software packages: RAMAS, ALEX, GAPPS, VORTEX, etc. These tools provide the computational framework for conducting PVA.

• Testing the approach:

  • Brook et al. (2000) conducted retrospective PVAs on 21 long-term data sets from birds and mammals (using the first ½ of data).

  • Demonstrated largely accurate results with good datasets, validating the use of PVA for conservation planning.

• Ecologically Functional Population size (EFP) vs. MVP: EFP considers the ecological roles and interactions of a species.

  • Maintaining interactions, fulfilling ecological roles is crucial for ecosystem health.

  • PVA can be used to calculate EFP of interacting species to ensure the persistence of ecological functions.

• Most models project future population sizes based on current population size and per capita birth and death rates, providing a basic understanding of population trends.

• Better modeling incorporates population regulation factors (food supply, competition, disease, predation, migration), which affect birth/death rates and population growth, allowing for more accurate predictions.

Modeling Approaches: Hierarchical Analysis

• Population regulation is a hierarchical process involving multiple levels of organization.

  • Individual level: Use of resources within a habitat, affecting survival and reproduction.

  • Landscape level: Regional trend in habitat availability and quality, influencing population distribution and abundance.

• Levels of factors affecting population size (BIDE). These factors operate at different scales and interact to determine population dynamics.

• Example: Sparrow birth and death rates are largely regulated by food supply at the individual level.

  • Sparrows live primarily in early successional habitats, with availability varying due to farming practices at the landscape level, illustrating the interplay between local and regional factors.

Modeling Approaches: Landscape Models

• Individuals move over the landscape, connecting populations and influencing gene flow.

  • Good and bad locations: Interconnectedness of populations is recognized and incorporated in landscape models.

• A landscape perspective is always better in management plans because it considers the broader ecological context.

• Landscape considerations are now being widely adopted:

  • Including: Source-sink and metapopulation dynamics, regional land use patterns (in and out of management units), whole watershed for aquatic systems.

  • Suitable habitat within a landscape (patches) when found within an unsuitable habitat matrix, highlighting the importance of habitat connectivity.

• Example: Bachman's sparrow breeds in both older-growth pine and clear-cuts but not middle-aged forests, showing large spatio-temporal variation in suitable habitat and the need for dynamic management strategies.

Modeling Approaches: Spatially Explicit Population Models (SEPM)

• SEPM incorporate actual locations of individuals and suitable habitat and consider the movement among them, providing a more realistic representation of population dynamics.

  • Landscape map: Visualization of habitat distribution and connectivity.

  • Projection of landscape change: Predicting future habitat availability based on various scenarios.

  • Simulation of population dynamics Accounting for spatial factors and individual movements.

• Example: Northern Spotted Owl simulations that vary only on the configuration of suitable habitat, demonstrating the impact of habitat fragmentation on population viability.

  • Scattered habitat leads to reduced connectivity and increased extinction risk.

Other landscape-level approaches

• Landscape species approach:

  • Focus on one species with a wide range (i.e., large carnivores) and its critical habitat to conserve entire ecosystems.

  • Combined with the human landscape (land uses, activities, jurisdictions, etc.) to address conservation challenges in a holistic manner.

  • Example: Y2Y grizzly bear, creating a landscape of connected suitable habitat that is feasible to conserve and promotes ecological integrity.

Alternative and future analyses

• Integrate the human population factor into landscape analyses (socioeconomics, future development plans/possibilities) to address the complex interactions between human activities and biodiversity.

  • Example: Panda in China’s reserves, where human land use and development impact habitat availability and connectivity.