Community Ecology and Biodiversity

Community: An assemblage of many populations that live in the same place at the same time.
- Can occur on a wide variety of scales and can be nested.
Community Ecology: The study of factors that influence the number and abundance of species in a community.
Ecosystem: A system formed by the interaction between a community of organisms and its physical environment.
- Ecosystem Ecology: The study of the flow of energy and production of biomass (the total mass of living matter in a given area).

One Health: The collaborative effort of multiple disciplines to achieve optimal health outcomes for people, animals, plants, and the environment.
- Involves protecting human, animal, and environmental health.
Key Partners: Centers for Disease Control and Prevention (CDC), National Center for Emerging and Zoonotic Infectious Diseases.

COVID-19 linked to the One Health Approach impacting human, animal, and environmental health.
Diagram illustrating correlation between COVID-19 (SARS-CoV-2) and ecosystem factors.

Analyzed data from 1940 to 2004 indicating that land use changes and agricultural industry changes were significant drivers of zoonotic diseases.
- Land use changes and agricultural changes accounted for over one-third of zoonotic disease events.

Transportation: Decrease in air and car commuting led to shutdowns in food transport and reduced recreational activities.
Food Production: Reduced food production resulted in lower demand for supply chains.
Field Science: Scientist and enforcement officers restricted from working in the field; important meetings postponed, impacting policy decisions.
Wildlife Impact: Reduced traffic led to fewer vessel strikes and road kills, and less commuting resulted in lower pollution levels, including noise and chemical emissions.
Local Economies: Collapse of food markets and supply chains increased local foraging by humans and contributed to increased burning and logging of forests, leading to habitat loss.
Enforcement Issues: Reduction in visits to protected areas limited funding for enforcement, allowing increased unauthorized fishing, logging, hunting, and harvesting.
Biodiversity Threats: Decline in exploitation led to increased wildlife abundance and survival, but reduced enforcement in protected areas created opportunities for illegal activities.
Local Insecurity: Declines in conservation funding and increased reliance on natural resources heightened biodiversity threats such as poaching and land conversion.

Species Richness: Refers to the number of species in a community; varies geographically, increasing from polar to tropical areas.
Latitudinal Gradient Hypotheses:
1. Species-Time Hypothesis: Communities diversify over time; temperate regions less diverse due to recent glaciation recovery.
2. Species-Area Hypothesis: Larger areas support more species due to larger populations and varied habitats.
3. Species Richness and Evolutionary Time and Area: Older and more widely distributed tree species host higher insect richness.
4. Species-Productivity Hypothesis: Greater plant production correlates with higher species richness; represented by evapotranspiration rate.

Shannon Diversity Index: Measures community species diversity; calculated as:
H' = - rac{ ext{Σ}(pi imes ext{log}(pi))}{n} where $p_i$ = proportion of individuals in species $i$ and $n$ = total number of species.

Succession Types:
- Primary Succession: Occurs on newly exposed sites not previously occupied.
- Secondary Succession: Occurs in areas that have supported life but experienced a disturbance.
Facilitation: Concept introduced by Frederic Clements that colonizing species alter the environment, making it more suitable for subsequent species.

Developed by Robert MacArthur and Edward O. Wilson focusing on species balance on islands through immigration and extinction rates.
- Equilibrium Number (S) reflects balance between immigration and extinction.
- Predictions include a positive correlation between island size and species richness, as well as distance from mainland impacting species diversity.

Trophic Levels: Levels of a food chain include primary producers, primary consumers (herbivores), secondary consumers (carnivores), and decomposers.
Food Chains: Typically short; usually less than six levels due to energy loss in transfers, governed by the laws of thermodynamics.
Biomass Production: Gross primary productivity (GPP) represents carbon fixed during photosynthesis.
Limiting Factors: Nitrogen and phosphorus can limit primary productivity; this is described by Liebig’s law of the minimum.

Stability and Productivity: Species diversity impacts community stability and productivity.
- Resistance: Capacity to tolerate disturbances.
- Resilience: Rate of recovery post-disturbance.

Community ecology is critical in understanding the health of ecosystems and addressing biodiversity loss. The joint impacts of human activity, climate change, and diseases such as COVID-19 emphasize the necessity for integrated approaches like One Health to promote sustainable outcomes for both the environment and human societies.