Humans & Ecosystems

Humans depend on ecosystems for:

-Food

-Habitat

-Oxygen and clean air

-Energy…

There are lots of ways humans have changed the Earth’s ecosystems. We will focus on the following

• Habitat change

• Overexploitation

• Pollution

• Invasive species

For each impact you should be able to answer:

1. How are humans impacting the ecosystem?2. Is this linked to the cycling of nutrients (carbon or nitrogen) impacted?3. How does this impact aquatic and terrestrial ecosystems?4. How does this impact the lithosphere, hydrosphere and/or atmosphere?5. How is the human impact changing the health of the ecosystem?6. Is the human interaction sustainable?

Invasive Species(in Canada) p59

• Species that are introduced to an ecosystem that were not originally present are considered EXOTIC species

• Often these species can thrive and their population increases greatly. They may even out-compete native species. These are then considered invasive. They can decrease biodiversity if they decrease the numbers of native species.

Check out www.invasive.org

Exotic SpeciesDandelion – introduced 1800’s. Settlers brought them from Europe because they thought they were a pretty plant.Also arrived at the same time: Norway maples, smallpox & measles among other things!

Invasive Species in OntarioPurple loostrife was a plant that people thought was pretty and started planting in small backyard ponds without considering the impact of the exotic species. It spread through waterways and has clogged up many wetlands and waterways due to its prolific production – 2-3million seeds a year and no native (in Ontario) animals to eat it. This plant was out-competing native plants for space and nutrients. To try to alleviate the problem scientists introduced another non-native species the seed weevil in 1994. This was an insect that would eat the purple loostrife and it was hoped would fit into the Southern Ontario food web.

Purple loostrife (Lythrum salicaria L.)

Invasive Species

• Asian carps (Silver carp, Bighead carp, Grass carp, Black carp):

http://www.youtube.com/watch?v=rPeg1tbBt0A

These are found in large numbers in the US (Illinois) but could follow waterways into the Great Lakes and they have the potential to outcompete native species like salmon, lake trout and walleye.

Invasive SpeciesEmerald Ash Borer Beetle introduced in 2007. Currently is attacking Ash trees in southern Ontario. In Kitchener conservationist are removing the trees in the hopes to starve the beetle and prevent it from spreading further north. The ash trees will ideally be replanted once the beetle is no longer such a problem. In the Windsor area woodpeckers have started to eat the ash borer and it is hoped that these birds will keep the ash borer beetle in check!CTV news cliphttp://kitchener.ctvnews.ca/kitchener-to-cut-down-hundreds-of-trees-as-emerald-ash-borer-battle-heats-up-1.1139834

More examples of Invasive Species – Zebra Mussels

Brought to Great Lakes on ships in their ballast water!

Invasive Species

Both round goby (Neogobius melanostomus) and zebra mussel (Dreissena polymorpha)

Exotic species are almost always introduced intentionally or unintentionally by human travel.Upcoming extensions…Preventing Invasive species – see p 100-101 in text

Endangered Species pp94- in text

• A species that faces extinction or extirpation (extinct in some areas).

Spotted Owl Grizzly Bear

Endangered Species

Species become endangered for a variety of reasons:

•Hunting/ poaching

•Habitat loss or fragmentation

•Overexploitation of a resource like water

•Disease

•Exotic species

• the vast majority of southern Ontario used to be one giant forest. Now much of it is farms and cities with small islands of forest scattered throughout.

• This is known as habitat fragmentation, where only small chunks of the original habitat are left interspersed between developed land.

• Overexploitation

• This is when a resource is used up faster than it can be replaced.

• A common example of this is overfishing.

• The cod fishery in Atlantic Canada collapsed in the 1990’s. The fishing industry got more efficient at gathering fish and gathered them all up. They took the young and the old and then there were none left. The cod population still has not recovered.

Endangered Species

• Once species populations become small it becomes difficult to find mates and inbreeding is an issue. This decreased genetic diversity makes organisms less adaptable to changes and diseases.

Endangered Species around the world

White RhinoHunted for it’s horn

Whale sharkCaught for it’s fins

Natural Resources

Canada is so fortunate to have a large variety of natural resources including:

-Metal deposits (gold, or mining copper…)

-Potash

-Oil sands

-Freshwater

-Forests

-Fisheries…

Human Impacts

Humans use these resources but we need to get them from their natural environment. This leads to our common practices of mining, logging (clear-cutting), diverting water for farming or dams, hunting, fishing. All of these cause changes to populations and habitats.

Habitat change

• This is the process by which humans alter a habitat enough so that native species can no longer live there.

• We alter habitats for a variety of reasons including cities, agriculture, dammed rivers etc.

Logging Forests

Clear-cutting: All trees are mechanically removed.

Selective cutting: only valuable trees are removed manually.

Clear Cutting- Less expensive to do

- Safer for workers

- Can choose what trees to re-plant

- Causes soil erosion and runoff of nutrients (soil quality decreases)

- Changes habitat

- Decreases biodiversity

Selective Cutting

Better ecological option but still:

•Destroys/changes habitat

•Decreases biodiversity

•Is more costly and more dangerous for workers

Why do humans log forests?

• Building materials

• Paper products

• Clear land for agriculture

• Clear land for roads and human habitation

• Get to materials under the land… mining, oil sands…

The nature of things:

http://www.cbc.ca/natureofthings/episode/billion-dollar-caribou.html @ 28 min

Rick Mercer Potash mininghttp://www.youtube.com/watch?v=ZKQmsr5m_uY

Fort McMurrayhttp://www.youtube.com/watch?v=HNSbiNxxlTQ

How does logging impact species?

• Decreases habitat

• Decreases food

• Fragmenting of forests – changes migration paths and breeding grounds

How do we decrease logging?• Recycle & choose to buy recycled

materials

• Reduce use of …

• This does not just happen on land either. Some fishing industries are clear cutting the ocean floor with bottom trawling nets that scoop up everything on the ocean floor and damage coral beds and many other primary producers.

Farming

Current practices in farming include:

- clearing land and planting monocultures of crops.

- clearing land and/or using grasslands to feed animals for human consumption

Farming

Farming also uses pesticides to kill off weeds that compete with crops (herbicides), and decrease pests that eat the crops (insecticides). These pesticides can affect non-target organisms and will decrease the biodiversity. Pesticides can also have unintentional effects if they follow a food chain – this is called bioaccumulation.

Farming and Fertilizers

Recall fertilizers are a way to add useful nutrients like nitrogen to the soil. If not used by the plants these nutrients can run-off the soil into nearby aquatic ecosystems. This increase in aquatic nutrients can lead to huge changes in the water – algae blooms, decreased oxygen, and increased organic matter in the water.

Algae Blooms

Effects of Human Activities on the Nitrogen Cycle

• Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

Figure 3-30Figure 3-30

Recall: A way of fixing nitrogen without fertilizers – crop rotation

Pollution (p58 in text)

• This is a substance added to the environment that produces a condition that is harmful to organisms.

http://www.cbc.ca/news/world/china-to-cough-up-283-billion-to-clean-up-air-pollution-1.1324866

• One example of pollution is CO2 gas created by internal combustion engines.

• Burning fossil fuels also releases nitrous oxides and sulphur oxides which cause brown smog and acid rain

• Point source pollution enters at a specific place from a specific source. Eg. factories, sewage etc.

• Non-point source pollution enters indirectly when snow or rain redistributes pollution into other areas.