8.2 Human Impacts on Ecosystems

Wetlands refer to areas with soil submerged or saturated in water for at least part of the year.
- This includes land areas submerged in standing water but shallow enough to support emergent plants.

Various plants have adapted to living in these wet conditions, including:
- Cattails
- Lily pads
- Reeds

Wetlands provide several essential ecosystem services, which can be categorized as follows:

Provisioning Services:
- Habitat for diverse animal species.
- Recharge of groundwater.
- Absorption of pollutants.
Regulating Services:
- Filtration of water (e.g., removing sediments and pollutants).
- Control of floodwaters.
- CO₂ sequestration, thereby contributing to climate regulation.
Supporting Services:
- Nutrient cycling which enhances the productivity of the ecosystem.
- Provides habitats for pollinators and pest control organisms.
Cultural Services:
- Recreation and tourism opportunities like fishing licenses and camping fees.
- Educational and research opportunities in ecology and environmental science.

Wetlands face numerous threats which can have detrimental impacts on their ecosystem services and longevity:

Pollution:
- Nutrients (such as nitrogen and phosphorus).
- Sediments which can cloud the water and disrupt aquatic life.
- Hydrocarbon pollutants (like motor oil).
- Pesticides and endocrine disruptors.
Development Activities:
- Wetlands can be filled in or drained for conversion to agricultural lands, urban development (like housing developments), or to create parking lots and roads.
- Water diversion upstream for flood control, agriculture, or drinking water can reduce the water flow to wetlands, causing them to dry up.
- Example: The Everglades are affected by such developments and water management practices.
Construction Activities:
- Infrastructure projects like flood control systems can result in reduced water flow to wetlands, thereby impacting water levels and health.
Overfishing:
- Disrupts the food web within wetland ecosystems, leading to increased pressures on prey species and decreases in fish predator populations.

Reef algae, particularly zooxanthellae, have varying temperature tolerances generally ranging between 24°C and 29°C.
Prolonged exposure to temperatures exceeding this range can lead to bleaching, where the algae expel the symbiotic relationship with coral, causing coral stress and mortality.

Overfishing: Results in the depletion of key fish species that maintain the health of coral reef ecosystems.
Coastal Development: Activities like mangrove removal and increased sedimentation can smother coral reefs and disrupt their growth.
Climate Change: Rising ocean temperatures lead to coral bleaching; increased CO₂ levels cause ocean acidification, affecting the calcium carbonate structures of coral.
Pollution: Runoff from agriculture and urban areas introduces excess nutrients and harmful substances into marine environments, which can lead to algal blooms and further stress coral systems.

Effects: Oil spills can have devastating impacts on coral reefs. They coat corals, blocking sunlight and disrupting photosynthesis in symbiotic algae, leading to coral decline and death.
Oil also introduces toxic compounds that can cause immediate harm to marine life and long-term ecological changes.

Methods: Cleaning methods include:
- Mechanical recovery: Using skimmers and vacuums to remove oil from the water surface.
- Bioremediation: Introducing bacteria that can metabolize and break down oil components.
- Chemical dispersants: Used to break down and disperse oil, but can have harmful effects on coral reefs and marine ecosystems if not properly managed.