3.2 3.2 How Humans Influence EcosystemsHow Humans Influence Ecosystems Human intrusion has caused many BC wetlands to Human intrusion has caused many BC wetlands to

disappear.disappear. In the past 100 years up to 70% of the wetlands in the lower Fraser In the past 100 years up to 70% of the wetlands in the lower Fraser

Valley have been lost.Valley have been lost. WetlandsWetlands are special ecosystems that contain are special ecosystems that contain

completely waterlogged soil for long periods of completely waterlogged soil for long periods of time.time.

wetlands contain high wetlands contain high biodiversity, and also biodiversity, and also filter many impurities filter many impurities out of the water.out of the water.

because they hold because they hold large amounts of large amounts of water, they can help water, they can help prevent flooding.prevent flooding.

““SustainabilitySustainability” of ” of EcosystemsEcosystems Definition #1Definition #1: “The ability for an : “The ability for an ecosystemecosystem to to

maintain ecological processes”.maintain ecological processes”. ie. the ecosystem stays healthy naturally ie. the ecosystem stays healthy naturally

Definition #2Definition #2: “: “PeoplePeople using an ecosystem to meet using an ecosystem to meet their needs today without reducing the function or their needs today without reducing the function or health of the ecosystem in the future”health of the ecosystem in the future”

Sustainable practices Sustainable practices

maintain, or even improve, maintain, or even improve,

healthy ecosystems.healthy ecosystems.

Returning young coho salmon to rivers near Port Alice can help maintain sustainability.

The Effects of Land and Resource UseThe Effects of Land and Resource Use All of the land around us, even in cities, was once a All of the land around us, even in cities, was once a

part of an ecosystem.part of an ecosystem. We use the land for things like urban development, We use the land for things like urban development,

agriculture, industry, mining and forestryagriculture, industry, mining and forestry

““Resource use” refers to the ways we obtain and Resource use” refers to the ways we obtain and use naturally occurring materials.use naturally occurring materials. Most products you use every dayMost products you use every day

involve the use of some natural involve the use of some natural

resources in their production.resources in their production.

The processing and export of resources like lumber, coal and sulphur are very

important to BC’s current economy.

Habitat LossHabitat Loss Humans have impacted natural ecosystems over the Humans have impacted natural ecosystems over the

past 150 years.past 150 years. because of human expansion, habitats have been lost or because of human expansion, habitats have been lost or

fragmented.fragmented. ““Habitat fragmentation” is the splitting of large habitats into Habitat fragmentation” is the splitting of large habitats into

many smaller ones, resulting in disrupted natural activities for many smaller ones, resulting in disrupted natural activities for plants and animals.plants and animals.

Habitat loss (left) and habitat fragmentation (right) reveal the effects of human activities on ecosystems.

The Effects of DeforestationThe Effects of Deforestation DeforestationDeforestation is the clearing or logging of forests for is the clearing or logging of forests for

human use.human use. some land is never reclaimed or replanted.some land is never reclaimed or replanted. agricultural crops that are planted are often one species = agricultural crops that are planted are often one species =

monoculturemonoculture This reduces biodiversity, and leaves the crop vulnerable to pests This reduces biodiversity, and leaves the crop vulnerable to pests

or disease.or disease. PolyculturesPolycultures, of many plant , of many plant

species, are more species, are more economically economically

and biologically diverse.and biologically diverse.

Deforestation is still occurring in Deforestation is still occurring in

many tropical rainforests.many tropical rainforests.

Deforestation results in Deforestation results in soil degradationsoil degradation (moving wind & water erode topsoil & (moving wind & water erode topsoil & leave bare land behind).leave bare land behind). Topsoil: the upper layer of soil, is where most Topsoil: the upper layer of soil, is where most

of the nutrients, water and air are found for of the nutrients, water and air are found for plant growth.plant growth.

The Effects of AgricultureThe Effects of Agriculture In fields left without crops, water & wind can cause In fields left without crops, water & wind can cause

erosion.erosion. In wet areas the soil can become compacted.In wet areas the soil can become compacted.

Soil particles are squeezed together Soil particles are squeezed together This is due to farm animals or vehicles.This is due to farm animals or vehicles. There is no room for water or air to enter the soil.There is no room for water or air to enter the soil.

Because of Because of soil compactionsoil compaction water runs water runs off the soil instead of soaking in.off the soil instead of soaking in. causes leaching.causes leaching.

AerationAeration, which involves removing, which involves removing

small plugs of soil, loosens small plugs of soil, loosens

soil & can reduce run-off.soil & can reduce run-off.

Resource Exploitation:Resource Exploitation:

= resource use= resource use Humans depend on resource Humans depend on resource

exploitation for jobs, materials,exploitation for jobs, materials,

food, shelter and energy.food, shelter and energy. Exploitation can lead to habitat loss, soil Exploitation can lead to habitat loss, soil

degradation & contamination of water supplies.degradation & contamination of water supplies. Many mining and resource exploitations require Many mining and resource exploitations require reclamationreclamation

efforts.efforts. Reclamation Reclamation attempts to reduce environmental impacts attempts to reduce environmental impacts

of exploitation, and tries to restore the original (or at least of exploitation, and tries to restore the original (or at least functional) habitats.functional) habitats.

Overexploitation:Overexploitation: the extraction of resources until they are the extraction of resources until they are

gone.gone. Can result in extinction Can result in extinction

Example: passenger pigeonExample: passenger pigeon

Food webs can be greatly affected for long Food webs can be greatly affected for long periods of time especially in periods of time especially in keystone keystone species species (species that greatly influence the population (species that greatly influence the population numbers and health of an ecosystem)numbers and health of an ecosystem)

Traditional Ecological Knowledge:Traditional Ecological Knowledge: In Aboriginal cultures it is passed down from In Aboriginal cultures it is passed down from

generation to generation.generation to generation. This knowledge reveals what past conditions This knowledge reveals what past conditions

were like, and also how the ecosystem and were like, and also how the ecosystem and humans interact.humans interact.

Knowledge is found in stories, songs, cultural Knowledge is found in stories, songs, cultural beliefs, rituals, community laws and traditional beliefs, rituals, community laws and traditional practices.practices.

Current ecological restoration and usage Current ecological restoration and usage guidelines often involve this traditional guidelines often involve this traditional knowledge from Aboriginal representatives.knowledge from Aboriginal representatives. Traditions such as the “Spring burn” allow for Traditions such as the “Spring burn” allow for

ecological renewal.ecological renewal. Fire suppression, enforced in BC for over 100 years, Fire suppression, enforced in BC for over 100 years,

has led to recent issues like the mountain pine has led to recent issues like the mountain pine beetle infestation and huge wildfire losses.beetle infestation and huge wildfire losses.

Take the Section 3.2 Quiz