3.2 How Humans Influence Ecosystems Human intrusion has caused many BC wetlands to disappear. In the past 100 years up to 70% of the wetlands in the lower Fraser Valley have been lost. Wetlands are special ecosystems that contain completely waterlogged soil for long periods of time. wetlands contain high biodiversity, and also filter many impurities out of the water. because they hold large amounts of water, they can help prevent flooding. Wetlands are the kidneys of the earth: removing up to 80% of nitrate, help regulate climate by retaining carbon. Bogs are like sponges Peat bog Bog wet muddy ground too soft to support a heavy body. They are frequently covered in ericaceous shrubs rooted in the sphagnum moss and peat. The gradual accumulation of decayed plant material in a bog functions as a carbon sink. Bogs occur where the water at the ground surface is acidic and low in nutrients.
Bog Bog wet muddy ground too soft to support a heavy body. They are frequently covered in ericaceous shrubs rooted in the sphagnum moss and peat. The gradual accumulation of decayed plant material in a bog functions as a carbon sink. Bogs occur where the water at the ground surface is acidic and low in nutrients.
Wetlands: Kidneys of the Earth Reduce nitrate concentration by 80% Retain carbon helps reduce climate change Peat very absorbantprevents flooding Dried peat source of fuel Blueberries and cranberries source of food Peat retains water and lowers pH also sold to garden nurseries
Cranberries grow in bogs
Burns Bog
Burns Bog on Fire
Human Activity 50-70% of original wetland habitat lost due to human expansion loss of biodiversity by reducing numbers of plant and animal species Concern: draining/drying out of wetlands will release carbon dioxide and methane into atmosphere
“Sustainability” of Ecosystems Definition #1: “The ability for an ecosystem to maintain ecological processes”. ie. the ecosystem stays healthy naturally Definition #2: “People using an ecosystem to meet their needs today without reducing the function or health of the ecosystem in the future” Sustainable practices maintain, or even improve, healthy ecosystems. Dichotomy between maintaining environment and meeting our needs. What is sustainable for environment does not necessarily mesh with our needs. Sustainable practices: tree planting, helping bees, tree planting. Returning young coho salmon to rivers near Port Alice can help maintain sustainability.
The Effects of Land and Resource Use All of the land around us, even in cities, was once a part of an ecosystem. We use the land for things like urban development, agriculture, industry, mining and forestry “Resource use” refers to the ways we obtain and use naturally occurring materials. Most products you use every day involve the use of some natural resources in their production. Tie this with our eco project Land use: how we use the land for urban development Resource use: how we obtain soil, wood water, gas oil and minerals The processing and export of resources like lumber, coal and sulphur are very important to BC’s current economy.
Habitat Loss Humans have impacted natural ecosystems over the past 150 years. because of human expansion, habitats have been lost or fragmented. “Habitat fragmentation” is the splitting of large habitats into many smaller ones, resulting in disrupted natural activities for plants and animals. Habitat Loss-destruction of habitats Habitat Fragmentation – plant pollination, seed dispersal wildlife movement (migration patterns), plant and animal reproduction Habitat loss (left) and habitat fragmentation (right) reveal the effects of human activities on ecosystems.
The Effects of Deforestation Deforestation is the clearing or logging of forests for human use. some land is never reclaimed or replanted. agricultural crops that are planted are often one species = monoculture This reduces biodiversity, and leaves the crop vulnerable to pests or disease. Polycultures, of many plant species, are more economically and biologically diverse. Deforestation is still occurring in many tropical rainforests.
Deforestation results in soil degradation (moving wind & water erode topsoil & leave bare land behind). Topsoil: the upper layer of soil, is where most of the nutrients, water and air are found for plant growth.
The Effects of Agriculture In fields left without crops, water & wind can cause erosion. In wet areas the soil can become compacted. Soil particles are squeezed together This is due to farm animals or vehicles. There is no room for water or air to enter the soil. Compaction hampers growth, increase run-off can occur. Causing excess nitrogen an d pollutant such as pesticides to the environment.
Aeration, which involves removing small plugs of soil, loosens Because of soil compaction water runs off the soil instead of soaking in. causes leaching. Aeration, which involves removing small plugs of soil, loosens soil & can reduce run-off.
Resource Exploitation: = resource use Humans depend on resource exploitation for jobs, materials, food, shelter and energy. Exploitation can lead to habitat loss, soil degradation & contamination of water supplies. Many mining and resource exploitations require reclamation efforts. Reclamation attempts to reduce environmental impacts of exploitation, and tries to restore the original (or at least functional) habitats.
Overexploitation: the extraction of resources until they are gone. Can result in extinction Example: passenger pigeon Food webs can be greatly affected for long periods of time especially in keystone species (species that greatly influence the population numbers and health of an ecosystem) Over fishing of cod, salmon, eco flip Over hunting of certain whale species (sperm and baleen) caused orcas to seek other prey like sealion and otters. Starting I 1970 seal pops declined until finally sea ooters. Lat e 1990s low sea otter (key stone species) numbers allow sea urchins to explode. Sea kekp declined 45% in a day
Traditional Ecological Knowledge: In Aboriginal cultures it is passed down from generation to generation. This knowledge reveals what past condition were like, and also how the ecosystem and humans interact. Knowledge is found in stories, songs, cultural beliefs, rituals, community laws and traditional practices.
Current ecological restoration and usage guidelines often involve this traditional knowledge from Aboriginal representatives. Traditions such as the “Spring burn” allow for ecological renewal. Fire suppression, enforced in BC for over 100 years, has led to recent issues like the mountain pine beetle infestation and huge wildfire losses. On prairie, dry, not many trees mostly grasses and shrubs. Fires would take everything out. Cree nation in Alberta used controlledburning to renew grasslandecosystems. Burning recycles nutrients and rejuvenates plant growth. Also done in BC forests by first nations. Take the Section 3.2 Quiz