Environmental Perturbation, Extreme Events & Drought

Environmental Perturbation

• Environmental perturbations are large-scale disturbances affecting areas from watersheds to the entire planet.
• Environmental impacts and pollution typically focus on smaller, local scales.
• Extreme events and natural disasters can significantly impact the environment and humans.
• Extreme events occur over short time scales (hours to weeks).
• Examples of extreme events: tornadoes, floods, heat/cold waves, wildfires, earthquakes, tsunamis, volcanic eruptions, tropical cyclones.
• Hurricanes occur in the Atlantic region, while typhoons occur in the Pacific region (both are tropical cyclones).
• Drought is a long-term precipitation deficit, worsened by population growth and water pollution.
• Drought can become a natural disaster when prolonged.
• Examples of lakes significantly reduced or lost due to drought: Lake Urmia (Iran), Lake Waiawa (Hawaii), Dead Sea (Israel/West Bank/Jordan), Scott Lake (Florida), Aral Sea (Kazakhstan/Uzbekistan), Lake Peigneur (Louisiana), Cachuma Lake (California), Lake Chad (Chad/Cameroon/Niger/Nigeria).
• Reduced lake size impacts: food supply, irrigation, domestic water, energy production, biodiversity habitat, flood control, and recreation.
• Deforestation, especially of tropical rainforests, leads to loss of biodiversity, increased greenhouse warming, and increased erosion.
• Forests store about 100 tons of carbon per hectare, released as carbon dioxide when logged or burned.
• Desertification is the damage to semi-arid lands by overgrazing and unsustainable agriculture.
• Causes of desertification: overgrazing, crop production, salinization from irrigation, water diversion, dam construction.
• Soil degradation includes loss of soil fertility, biodiversity, and production capacity.
• Approximately one-third of the world's farmable land has been lost in the last four decades.
• Causes of soil degradation: agriculture, industrial and commercial pollution, urbanization, overgrazing, unsustainable practices, climate change.
• Overfishing has led to the collapse of major ocean fisheries since the 1950s.
• "Fishing down the food chain" simplifies marine ecosystems, impacting future fish and marine mammal populations.
• Example: Overharvesting of haddock, cod, and mackerel in Alaska reduced stellar sea lion populations.
• Krill fishing in Antarctica threatens species that depend on krill for food (penguins, whales, squid, fish).
• Coastal degradation and coral reef destruction are major concerns.
• Coral reefs host 20% of marine life, but 70% may be lost in coming decades.
• Aquaculture in sensitive ecosystems like mangrove swamps can cause environmental damage.
• Wastewater from fish farms can over-fertilize coastal waters, leading to algal blooms and fish kills.
• High population concentrations along shorelines lead to the loss of coastal ecosystems like seagrass meadows.
• Loss of coastal ecosystems eliminates breeding grounds for fish/crustaceans and feeding for birds.
• Coral bleaching occurs when corals expel symbiotic algae (zooxanthellae) under stress, especially heat stress.
• Silt runoff from land conversion forms "marine snow" that smothers and kills corals.
• Chlorofluorocarbons (CFCs) released into the atmosphere deplete the ozone layer.
• Species extinction driven by poaching, habitat destruction, invasive species, pollution, and global warming.
• Over 19,000 plant species and 5,000 animal species are classified as endangered.
• Climate change from heat-trapping gases emitted by fossil fuel burning is warming the Earth.
• Population growth is increasing the number of people per area due to natural increase and net migration.
• Global population increased from 2.5 billion to 7.5 billion between the 1950s and 2017.
• World population is expected to reach 9.7 billion in 2050.
• Industrialization leads to mass production, pollution, and land conversion.
• Urbanization increases the proportion of people in urban centers.
• Main causes of urbanization: rural-urban migration and natural increase.
• Urbanization can improve socio-economic conditions but can also lead to environmental and social problems if unmanaged.

Reclamation & Restoration

• The "four R's" for addressing disturbed systems are Reclamation, Remediation, Rehabilitation, and Restoration.
• Reclamation returns a site to productive use.
• Remediation removes or treats contamination to reduce risks.
• Rehabilitation focuses on improving site conditions to recover ecosystem services.
• Restoration is a general term for activities to improve site conditions.
• Ecological restoration assists the recovery of a degraded, damaged, or destroyed ecosystem.
• Reclamation and remediation are human-centric, focused on reducing health risks and supporting human activities.
• Reclamation, remediation, and rehabilitation can be part of ecological restoration projects.
• Land reclamation methods include surface grading/contouring, surface covers/caps, revegetation, and soil treatment.
• Surface contouring reshapes the land to create a stable and natural-looking landscape.
• Surface covers and capping limit water infiltration, control air entry, reduce erosion, support vegetation, and contain contamination.
• Soil caps are soil spread on surface, while geotextiles are permeable fabrics that allow water passage.
• Impermeable caps prevent percolation.
• Hardened covers reduce erosion and improve stability.
• Revegetation limits water infiltration, reduces erosion, minimizes contaminant migration restores habitat, and enhance aesthetics.
• Types of soil treatment include lime amendments for acidic soils and drainage improvement for saline soils.
• For soils with metal or organic contaminants, excavation/replacement, soil washing, and hydro-remediation can be used.
• Aquatic reclamation includes physical action, shoreline stabilization, stream channel modification, dredging, water treatment, sediment treatment, aquatic plan management or biomanipulation.
• Natural restoration is allowing an ecosystem to heal itself without active management.
• Active ecological restoration is necessary when natural recovery is insufficient.
• Guiding principles and best practices have been developed by the Society for Ecological Restoration.