Human Impacts to Biodiversity

Disturbances

• Disturbances: events that produce severe physical impacts on a habitat Examples: storms, earthquakes, human activity
• Can drastically lower species population
• May disrupt whole ecosystem

• Pulse disturbances: Short term, immediate disturbances
• Windstorms
• Floods
• Wave activity
• Fire
• Sudden increase in the number of herbivores in the habitat Example: locust
• Disease outbreaks
• Introduction of invasive species.

• Press disturbances: Long term, persistent disturbances
• Climate changes
• Geological processes Examples: mountain formation, continental movement, change in river flow
• Extinction of prey or mutualist

• Disturbance Regime: the type, frequency, and the severity of the disturbance
• Succession: how the community responds to the new habitat created by the disturbance
• Primary succession: when all life was wiped out Example: glacier melts and exposes bare rock for the first time
• "Starting from scratch"
• Secondary succession: when only some life was wiped out Example: Fire burns forest, but leaves the soil and seeds intact

• Pioneer species: first organisms to re-colonize after disturbance
• Species with high environmental tolerance
• First - Lichens
• Second - Annual plants and grasses
• Third - larger plants, insects, small mammals, birds
• Climax Community: when the ecosystem reaches equilibrium
• Not much change in species ("settles")
• intermediate disturbance hypothesis (IDH): intermediate levels of disturbance supports the greatest diversity
• At high levels of disturbance all species are at risk of going extinct
• At intermediate disturbance, species that thrive at both early and late successional stages can both exist
• At low levels of disturbance, diversity decreases because competitive exclusion increases

Photo by Sciencerelatedusername | CC BY

Agriculture & Biodiversity

Monoculture Farming

• All plants are genetically similar or identical
• Causes decreased soil quality
• Farmers need to use pesticides and herbicides frequently
• Pest species are a growing problem
• Pests = insects or "weed" plants that harm crop plants and decrease crop yields
• Example: The Irish Potato Famine was caused by monoculture grown potatoes that were killed by a pest fungus

Monoculture & Climate Change

• Pest species thrive in higher temperatures
• Accelerated development and reproduction
• Reduced need for cold/freeze tolerance or avoidance
• Increased pest species range into Northern regions
• Pesticides have decreased effectiveness at higher temperatures causing farmers to increase the rate of pesticide use
• More frequent usage selects for pesticide resistance
• Scientists have been, and are currently, working on genetically engineered crops to withstand high pesticide use and concentrations

Monoculture Forest Farming

• Logging companies plant the same species of tree in a large region for future clear-cutting
• All trees are the same age, so decreases diversity of wildlife and microbes
• Decreases soil quality

Polyculture Farming

• Increased diversity of species decreases reliance on pesticides
• Different plant species have varying pest defence mechanisms
• More resilient to disturbance
• Provides biological control
• Have higher crop yields than monoculture farming

Human Travel and Living & Biodiversity

Habitat Loss

• Habitat loss is the process where a habitat becomes unable to support its historically native species
• Habitat Destruction
• When none of the native species can be supported by the current land usage or land quality
• Causes: deforestation, bottom trawling of the ocean floor, filling in wetlands for urbanization, mining of fossil fuels, flooding for dam building
• Habitat Degradation
• When some habitat is of quality enough to support some native species, however many or most species are not supported
• Causes: invasive species, urban sprawl, overfishing, over-logging, pollution, climate change
• Habitat Fragmentation
• When the historical range of a species is interrupted by human activities causing habitats and populations to become smaller and more isolated
• Causes: building highways and roads, urbanization, urban sprawl, invasive species, waterway diversion

Solutions to Habitat Loss

• Habitat Degradation/Destruction
• Strict regulations for logging, fishing and hunting
• Stopping or reversing climate change
• Culling invasive species
• Investing in sustainable urbanization planning
• Educating local communities about sustainable practices and the importance of the biodiversity in their region
• Habitat Fragmentation
• Protect natural lands
• Wildlife corridors
• A strip or area of natural habitat connecting wild populations otherwise disconnected due to farming, roads or dams
• Sufficient buffer zones must be considered to be successful
• Particularly important for large mammals with wide species ranges