Negative Human Impacts on biodiversity

Habitat change

Invasive species

Pollution

Pesticide

Overexploitation

Climate change

Habitat change

Habitat loss Definition: Loss of natural ecosystems Human activity: conversion into farmland, urban

sprawl, transportation routes Fragmentation

Definition: Dividing up of a region into smaller parcels or fragments

Edges of an ecosystem are more susceptible to damage by outside influences

Fragmentation increases the perimeter

Factors that improve sustainability of habitat fragments

Factor Explanation Which is better?

Size Large versus small areas

Number Same total area but different number of fragments

Proximity Distance between fragments

Connectedness Whether corridors connect fragments together

Integrity Amount of outside access to habitat

Factors that improve sustainability of habitat fragments

Factor Explanation Which is better?

Size Large versus small areas Larger size

Number Same total area but different number of fragments

One large area

Proximity Distance between fragments Closer together

Connectedness Whether corridors connect fragments together

Corridors that permit migration between fragments

Integrity Amount of outside access to habitat

Fewer roads/trails

Global impact of habitat change

On a global scale, habitat loss and fragmentation are second to climate change as the most serious threat to sustainability of natural terrestrial ecosystems

In the Amazon, the world’s largest remaining rainforest is being cleared and burned to create pasture for cattle sold to foreign markets

Reducing demand for agricultural products produced in tropical regions can reduce rainforest habitat loss

Aquatic ecosystem: Loss of wetland

Human activity Impacts

Draining wetlands for urban expansion and agriculture

Commercial fishing and dredging to create deeper water for boats

Replacing natural vegetation along coastlines and waterfronts

Aquatic ecosystem: Loss of wetland

Human activity Impacts

Draining wetlands for urban expansion and agriculture

Loss of habitat

Commercial fishing and dredging to create deeper water for boats

Disruption of bottom-dwellers and spawning beds

Replacing natural vegetation along coastlines and waterfronts

Shoreline erosionLoss of breeding areas

Invasive Species

Exotic species: non-native species Usually exotic specie fail in a new

environment because it has been removed from its tolerance limits for all abiotic factors

Invasive species: exotic species that grow rapidly, spread and have a negative effect on the environment

Examples: carp, earwig, starling (bird)

Why exotic species become invasive

Growth of exotic species is unchecked due to: lack of population controls in the new

environment that were present in the old environment (e.g. predators, disease)

native species does not compete well with the exotic species

Impact of Invasive species

Ecological: compete with native species, leading to their population decline; alter nutrient cycles

Economic: lower crop yields; disease and pests may destroy livestock/crops

Health: disease-causing organisms; pesticide use

Tourism: choked waterways rendering them impassable to boats; negative impacts on recreation

Control Methods on Invasive species

Chemical: pesticides Mechanical: physical barriers or removal

Plants: Cut down, burned, removed by hand Animals: Hunted, trapped

Biological: using intentionally introduced organisms Invasive plant: purple loosestrife Biological control: 3 species on insects that feed

on it without feeding on native plants

Pollution

Toxic materials that are release into the environment

Examples: Purposeful pollutants: pesticide, fertilizer By-products: car exhaust, product

packaging

Acid Precipitation

Sulfur dioxide and nitrogen oxides produced in industrial processes and burning fossil fuels combine with water vapour to form acids

Why is the Canadian Shield more susceptible to the effects of acid rain? Certain minerals (e.g. limestone) can

neutralize acid Limestone is often found near lakes The Canadian Shield is made of

granite

Effects of acid precipitation

Lowers the pH of water and soil Acid leaching, nutrients in soil depleted Speeds up corrosion of metals Dissolves materials on building structures Ironically, acid lakes are desirable for

recreation. Why? Few organisms live in them So they appear clear and clean

Solution to acid precipitation

Wrong way: “Solution to pollution is dilution”

Concentration of pollutants is decreased by mixing them with large volumes of air or water

Although effects were less severe it spread over a greater area

Oil Spill

Oil is toxic, slow to break down, difficult to clean

Sea birds ingest it when cleaning themselves

Bird feather and seal fur lose their ability to insulate when covered with oil

Methods to clean oil spills

Skim/vacuum Bioremediation: microorganisms that are

capable of feeding on oil Burn: oil lit on fire to prevent it from sinking

or washing up on shore, but it pollutes the air

Dispersal agent: break up oil into small droplets using detergents allowing it to be washed out to sea and dispersed

Pests

Pests: organisms that people consider harmful or inconvenient

Agricultural pests: organisms that compete with or damage crop species

Examples: weeds, insect, mice No pests exist in nature

Pesticide

Chemicals designed to kill pests Herbicides: kill plants Insecticide fungicide

Characteristics of Pesticides

Persistence: how long the pesticide remains active in the environment

Is long or short persistence better?

Characteristics of Pesticides

Targeted: ability to kill only the intended pests

Broad-spectrum pesticides: effective against a wide range of species E.g. DDT toxic to most insects

Narrow-spectrum pesticides: effective against a limited number of species E.g. Bt (Bacillus thuringiensis), derived from

bacteria, toxic only to caterpillars, beetle larvae and fly larvae

Is broad or narrow spectrum better?

Case study: DDT

Island of Borneo, 1995 Malaria problem DDT spray to control mosquitoes DDT also killed wasps

Caterpillar wasps Caterpillars ravaged thatched homes

DDT also killed roaches Roach Lizards cat (death!!!) Rat population increased Rats carry fleas which carry the plague

Bioaccumulation & Bioamplification

Some pesticides are not broken down or eliminated

Thus you can have an accumulation of pesticides in… an individual organisms in a food chain as one organism eats

another

Bioaccumulation An increase in the concentration of a chemical

in an organism over time, compared to the chemical's concentration in the environment.

Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.

A normal and essential process for the growth and nurturing of organisms.

All animals bioaccumulate vital nutrients (e.g. vitamins A, D and K, trace minerals and essential amino acids)

Uptake

Entrance of a chemical into an organism

Uptake methods: breathing swallowing absorption through the skin

Factors that affect bioaccumulation

Concentration in the environment Duration of exposure Uptake rate

concentration of the chemical in the environment compared to an organism’s cells

tend to move from areas of high concentration to areas of low concentration (diffusion)

Lifetime of organism Anatomy of organism Solubility of pesticide (water soluble is more

easily excreted than fat soluble)

large, fat, long-lived individuals with low rates of metabolism or excretion of a chemical will bioaccumulate more than small, thin, short-lived organisms.

Thus, an old lake trout may bioaccumulate much more than a young bluegill in the same lake.

Bioamplification / Biomagnification

A process that results in the accumulation of a chemical in an organism at higher levels than are found in its food.

It occurs when a chemical becomes more and more concentrated as it moves up through a food chain.

An animal at the top of the food chain, through its regular diet, may accumulate a much greater concentration of chemical than was present in organisms lower in the food chain.

Algae water flea minnow trout eagle/human

For fish and other aquatic animals, bioaccumulation occurs after uptake through the gills or skin.

Storage: means the deposit of a chemical in body tissue or in an organ.

Example of bioamplification

Soil nutrients earthworms robins

DDT bioamplification In soil: 10 parts per million (ppm) In earthworms: 141 ppm In robins: 444 ppm

Consequences of Bioamplification

death abnormal behavior decreased ability to reproduce decreased resistance to disease

Resistance

Pests can develop resistance against pesticide

Individuals that survive (are resistant) will pas on their resistance to their offspring

Sustainable techniques of controlling pests

Biological control Crop rotation Altered timing: plant and harvest to

avoid peak pest populations Baiting pests: pheromones can

confuse mating insects

Integrated pest management (IPM)

Takes advantage of all types of management methods

Goal is to maximize efficiency, keep costs low, reduce harm to environment

Overexploitation

Definition Require consumption and resource

management

Forestry Practices

Clear-cutting: removal of all or most of the trees in a given area Takes large blocks or strips

Shelterwood cutting: mature trees harvested in series of two or more cuts Long narrow parallel strips

Selective cutting: periodic harvesting of selected trees Performed on private woodlots Where there is high values for individual trees or

where appearance of forest is highly value

Comparing forest management practices

Practice Advantage Disadvantage

Clear-cut

Shelterwood

selective

Comparing forest management practices

Practice Advantage Disadvantage

Clear-cut cheap Regenerate with seedlings

Forest of even-aged trees

Shelterwood Regenerate under shelter of remaining trees

selective Uneven-aged system

Least ecological impact

Most costly

Forestry Management

Fire suppression - good or bad?

Wildlife Management

Managed hunts to control populations First Nations and Inuit people

harvested wildlife in a sustainable way

Stewardship

Taking responsibility for managing and protecting the environment

Past: arrival of European settlers were more interested in resource as a source of revenue

Types of artificial ecosystem

Agroecosystem: Farms Urban ecosystem: cities, roads

Comparing natural vs artificial

Natural Artificial

Abiotic features

Biodiversity

Ecological cycles

Human use

maintenance

Comparing natural vs artificial

Natural Artificial

Abiotic features uniform

Biodiversity less

Ecological cycles

Altered

Human use Intensive

maintenance extensive