Reconnecting Nature and Environmental Risk

Islands and Habitat Fragmentation

• Darwin's Inspiration: The distinct mockingbird species on the Galápagos Islands inspired Darwin's ideas about the origins of species.

• Island Biogeography: MacArthur and Wilson focused on species extinction, generalizing geographical islands to habitat islands--areas suitable for a species surrounded by inhospitable landscapes.

• Island Size and Species Count: Small islands have fewer species than larger ones.

Human Impact on Landscapes

• Habitat Fragmentation: Human actions fragment landscapes, creating unintentional experiments in local extinction.

• Amazon Deforestation Study: A 40-year study in the Amazon showed that small forest fragments lost bird species more quickly than larger ones.

• Global Extinctions: Extinctions concentrate in biodiversity hotspots where human actions destroy and fragment habitats with concentrations of small-ranged species.

Problems of Small Populations

• Demographic Accidents: Small populations face high probabilities of skewed sex ratios and mortality.

• Genetic Concerns: Inbreeding in small populations leads to increased relatedness among individuals.

• Climate Disruption: Fragmented landscapes impede species movements to higher latitudes and elevations in response to climate change.

• Restricted Animal Movement: Fences and barriers prevent animals from dispersing to find safe habitats and water sources, leading to deaths.

Reconnecting Nature

• Conservation Goal: Conservation science aims to prevent extinctions by reconnecting landscapes.

• Assessing Interventions: Ecologists face a dilemma as controlled experiments are smaller in scale than conservation problems.

• Species-Specific Actions: Genetic rescue, such as introducing female panthers from Texas to Florida, can save small populations.

• Landscape Interventions: Habitat corridors benefit many species simultaneously and operate on a wide range of scales.

• Highway overpasses and tunnels allow movement, potentially diminishing genetic and demographic problems in isolated populations.

Types of Interventions

• Infrastructure Crossings: Building connections above or under highways and railroads to facilitate wildlife movement and reduce collisions.

• Habitat Restoration: Deliberately restoring habitats to reconnect previously isolated fragments.

• Transient Failures: Habitat fragmentation experiments had temporary comebacks when cleared areas grew back, creating temporary corridors.

Small-Scale Experiments

• Savannah River Experiment: A study with 27 patches of early successional habitat within pine forests examined corridor effects on species movement and diversity.

• Observed Benefits: Corridors increased butterfly movement, pollen and seed dispersal, plant and insect species richness, and genetic variability.

Overpasses, Underpasses, Tunnels, and Bridges

• Extensive Implementation: These interventions connect large habitat remnants across six continents.

• Target Species: Diverse species, including ungulates, mammals, bats, reptiles, amphibians, birds, and insects, utilize wildlife crossings.

• Monitoring Techniques: Passive surveillance (camera traps, track reading) and active observation are used to gather data on species utilization.

• Documented Examples: A review documented 351 examples of terrestrial infrastructure with 990 separate structures facilitating wildlife movement.

Corridor Characteristics

• Infrastructural Corridors: Artificial structures made of concrete, metal, or wood with replanted vegetation.

• Underpasses: Most numerous class (54%), including tunnels and culverts, prevalent in Europe and North America.

• Overpasses: Eclectic mix, including rope bridges and glider poles, more frequent in Europe due to social commitment to wildlife and in boreal forests to reduce collisions with large mammals.

Corridor Intentionality

• Intentional Corridors: Designed for general wildlife use or specific species, accommodating habitat idiosyncrasies.

• Incidental Corridors: Built for other purposes (drainage, human traffic) and later adapted for wildlife crossings.

Corridor Effectiveness

• Ongoing Question: Corridor effectiveness is evaluated from economic and scientific perspectives.

• Success Measurement: Monitoring social impacts (reduced collisions) and species dispersal and diversity.

• Successful Example: A corridor in Rio de Janeiro state, Brazil, showed species (crab-eating fox) using it shortly after completion.

Factors for Effective Corridor Design

• Location Matters: Ineffective bat crossings due to misalignment with established flight routes.

• Structure Matters: Wider, shorter, open crossings are more effective for mule deer, elk, and moose.

  • Culvert \ Length \propto \frac{1}{Success \ Rate}

• Species Differ: Some species (bandicoots) frequently use culverts, while others (koalas) use them sparingly.

• Habitat Matters: Overpasses with suitable surrounding habitats and features like native vegetation, logs, pools, and streams are more successful.

Genetic Rescue

• Limited Evidence: Few tests document genetic rescue effected by corridor construction.

• Australian Study: Only one of four wildlife crossings for squirrel gliders promoted gene flow.

• Banff National Park Study: Wildlife crossings allowed gene flow between grizzly and black bear populations.

Corridors of Natural Habitat

• Unintentional Experiment: Temporary funding shortage in the Amazon fragmentation study led to forest regrowth, creating corridors and allowing species to return.

• Deliberate Habitat Restoration: Restoring natural corridors requires buying and protecting land.

• Restored Example: A restored habitat in Rio de Janeiro state, Brazil, reconnects a once-isolated reserve, with species like puma and golden lion tamarin using it.

Large-Scale Habitat-Corridor Programs

• Collaborative Initiatives: Local, regional, state, national, and international initiatives to connect habitat over large landscapes.

• Yellowstone to Yukon (Y2Y): An ambitious initiative that has expanded protected lands along a 3,200 km span.

• Replacing barbed wire with wildlife-friendly fencing to allow large mammal dispersal.

• Kavango Zambezi Transfrontier Conservation Area: Aims to allow wildlife management over five countries, but faces challenges with fences.

Lessons and Gaps in Knowledge

• Scope of Efforts: Efforts to reconnect nature encompass various species and ecosystems, with structures ranging from culverts to multinational plans.

• Effectiveness of Large-Scale Connections: Hard to demonstrate effectiveness beyond allowing movement.

• Impact on Species Movement Upslope: Limited studies on the impact of connections on allowing species to move upslope to avoid global heating.

• Deliberately Planted Habitat Corridors: Few examples, but substantial conservation potential, requiring long-term comparisons.

• Contentious Issues: Reconnecting nature may become contentious due to concerns about fences and their impact on certain species.

Environmental Risk in an Age of Biotic Impoverishment

• Biodiversity's Importance: Ecological, evolutionary, and environmental research has pointed to biodiversity's importance in influencing the stability and functioning of ecological systems.

• Shifting Focus: Redirecting ecology's emphasis from ecological stability to environmental risk could help bring bio-functional ecology research more into the environmental arena.

• Managing Biodiversity as Natural Capital: Biodiversity could be managed as a natural capital asset in a portfolio of social, human, produced, and financial capital assets.

• Motivation to Preserve Biodiversity: Environmental risk more accurately captures people's motivation to preserve and manage biodiversity than ecological stability.

Mariposa —> comida, descanso con flores

Introduccion de especies: mantener flujo genetico

• Pantera de florida tiene poca diversidad genetica: mas hembras que macho introducen hembras solamente a la poblacion

• Antelopes de africa: mantener ratio

Faulure —> se reforesta

Camaras (comportamineto), corridore, genetica s

Limitacion no hay sufcieicentes datos para saber si esta funcionando

Distancia impacta

La zona del carso y noreste pueden ser corredores

Fincas privadas sirven como corredores

Migracion - organismos vives se mueven

Areas llanas estan calientes y suben a las monatanas —> Cambio climatico

• Plantas semillas crezcan mas fresco etc