Negative Human Impacts on biodiversity
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Transcript of Negative Human Impacts on biodiversity
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