ATP: Lesson - Human Impacts on Wetlands (Topic 8.4) 📖
⏳ Estimated Reading Time: 7 - 9 minutes
Describe the impacts of human activity on wetlands and mangroves.
Wetlands
Wetlands are areas where water covers the soil all or part of the time. In the past, wetlands were thought of as wasted lands because they were too wet to grow crops, build houses, and served as habitats for species that we usually think of as pests, such as mosquitos and snakes. We now know that wetlands serve critical ecological functions.
Wetlands tend to have both submerged aquatic vegetation (SAV) and emergent aquatic vegetation (EAV). SAV are plants that grow underwater and only their flowers, if any parts of them, emerge from under the water. Emergent aquatic vegetation are plants where their photosynthetic parts are exposed, at least at low tide.
Types of wetlands include marshes (salt, brackish, intermediate, and fresh), swamps, bogs, and mangroves. In this lesson, we will focus on salt marshes and mangroves.
Salt marshes are dominated by soft-stemmed grasses and are typically shallow. During dry times, the salinities in marshes are higher than during the rainy season, when runoff from the land dilutes the salts in the water, lowering the salinity. They occur on quiet coastlines around the globe, from sub-arctic zones to warm, temperate zones.
Mangrove swamps are dominated by salt-tolerant woody-stemmed trees. Mangrove trees must have their roots exposed to air at least once/day. This is why many mangrove trees have raised roots that stick out of the sediment. These ecosystems occur worldwide in tropical and subtropical climates.
Wetlands are areas where water covers the soil, either part or all of the time.
Ecological Functions of Wetlands
Wetlands are highly productive ecosystems that also serve a variety of ecological functions. Explore the presentation below to learn more about each of these ecological functions:
Recognizing the value of wetlands and mangroves is the first step in protecting these unique habitats for future generations.
Wetlands provide a variety of ecological services, including water purification, flood protection, water filtration, and habitat.
Threats to Wetlands
If you remember our discussion of HIPPCO, we can use this acronym to help us understand the threats to wetlands. Explore the list below, opening each threat to learn more about how HIPPCO affects wetlands.
H: Habitat Destruction 🚧 (click to reveal)
A large portion of the world’s wetlands have been lost to development for housing, industry, and agriculture.
🌾 Drainage for Agriculture: Wetlands are often drained to make way for agricultural land. This not only destroys the habitat but also disrupts the natural water storage and filtration systems.
🏢 Urban Development: The construction of housing, roads, and other infrastructure leads to the filling in and paving over of wetlands, resulting in loss of biodiversity and increased flood risk.
💧 Water Diversion: Dams and water diversions change the natural flow of water into and out of wetlands, which can lead to habitat fragmentation and reduced water quality.
In the past, we built ditches to drain marshes. After draining the marshes, we filled the marsh to build on it, use the land for agriculture, or create freshwater ponds. However, when marshes are drained, we lose all of the beneficial functions of the marsh and these areas tend to “want” to fill back up with water, making flooding a perpetual issue.
I: Invasive Species 🐍 (click to reveal)
Non-native species can...
🐀 Outcompete native flora and fauna
🐍 Prey on native species
🧬 Hybridize with native species
🦠 Introduce new diseases
which can alter food webs, cause a loss of biodiversity, modify the habitat, reduce genetic diversity, and impact human services from wetlands, such as bird-watching, water distribution, navigation, and resource provisioning.
P: Population Growth 👨👩👧👦 (click to reveal)
Human population growth is often the underlying cause of all other aspects of HIPPCO. As our population grows, we....
🌾 Drain for Agriculture
🏢 Drain for Urban Development
🏠 Drain for Housing
🗑️ Produce more waste and runoff, which runs into wetlands
🎣 Exploit resources in wetlands for food
💧 Divert water for domestic and agricultural use
🛣️ Build infrastructure such as roads and dams
🌍 Increase the speed and severity of climate change
P: Pollution 🛢 (click to reveal)
Wetlands suffer from pollution in several ways...
🌾 Agricultural runoff containing pesticides and fertilizers
🛢 Industrial discharge, such as heavy metals
⛽️ Urban runoff can carry oil, heavy metals, and trash into wetlands
🚽 Sewage overflow during heavy rain events
🧴 Plastic pollution
🌧️ Acid Rain
C: Climate Change 🌎 (click to reveal)
Climate change can threaten wetlands in several ways...
🌧️ Changes in precipitation flooding or drying out wetlands
🌡️ Increased temperatures causing increased evaporation
🧂 Increased salinity caused by sea level rise
♻️ Warmer temperatures can change wetlands from carbon sinks to sources
🌊 Flooding wetlands due to rising sea levels
❌ Species loss as habitats become unsuitable for native residents
🪨 Increased erosion and sedimentation
O: Overexploitation 🎣 (click to reveal)
Wetlands are continually exploited for human gain....
💧 Excessive withdrawal of water for agricultural, industrial, or domestic use
🎣 Unsustainable fishing and hunting
🌱 Overharvesting of resources, such as plants, peat, or fish
🏘️ Draining for agriculture, urban development, or housing
🌾 Pollution from intensive agriculture
🧳 Tourism pressure
🚨 Illegal activities such as poaching and unauthorized use
Threats to wetlands and mangroves include commercial development, dam construction, overfishing, and pollutants from agriculture and industrial waste.
Wetlands must be covered with water for at least part of the time.
When trying to decide human impacts on any ecosystem, refer back to HIPPCO, which can help you determine impacts.
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