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B. Biology: Sustainable Ecosystems and Climate Change · Sustainable Ecosystems and Climate Change

Climate Change Impacts on Ecosystems, and Initiatives to Fight Back

B1.1 B2.6 A2.3 A2.4About 75 minutes
Learning goals
  • I can assess the impacts of climate change on the sustainability of local (Ontario) and global ecosystems.
  • I can explain which species and ecosystems are most vulnerable, and why.
  • I can describe local, national and global initiatives for combatting climate change.
  • I can distinguish mitigation from adaptation and evaluate solutions using criteria.

Words to know

mitigation
Actions that reduce the causes of climate change by cutting greenhouse gas emissions or increasing carbon sinks.
adaptation
Actions that reduce the harm from climate change impacts that are already happening or expected.
net-zero emissions
When any greenhouse gases released are balanced by an equal amount removed from the atmosphere.
Paris Agreement
A 2015 international agreement to keep global warming well below 2 °C above pre-industrial levels and to pursue efforts to limit it to 1.5 °C.
habitat corridor
A strip or network of natural habitat that connects separate areas so species can move between them.
nature-based solution
Using healthy ecosystems (forests, wetlands, grasslands) to cut emissions or help people adapt, for example restoring wetlands to store carbon and soak up floods.
vulnerability
How likely a species, ecosystem or community is to be harmed, based on exposure, sensitivity and ability to adapt.

Remember from earlier lessons

You now know how ecosystems stay in balance (Lessons 1 to 8), how human activities upset that balance (Lesson 9), why the climate is warming (Lesson 10) and what the indicators show (Lesson 11). This lesson pulls these together to assess the impacts on ecosystems near home and around the world, and then turns to what people are doing about it.

Let's start on Hudson Bay

The polar bears of Hudson Bay, including bears that live along Ontario's northern coast, hunt seals from the sea ice. When the ice melts in summer, they come ashore and live mostly off their stored fat until the bay freezes again in late fall. As the climate warms, the ice season is getting shorter, so the bears have less time to hunt and must go longer without food. Scientists have linked the longer ice-free season to declines in some Hudson Bay polar bear populations.

One change in the hydrosphere (sea ice) ripples through a food web: seals, bears, Arctic foxes that scavenge bear kills, and the people who live alongside them.

Impacts on ecosystems close to home (Ontario)

  • Great Lakes and inland lakes: warmer water, shorter ice seasons, longer summer layering, more algae blooms, and less habitat for cold-water fish such as lake trout and brook trout. Warm-water fish and some invasive species may benefit.
  • Forests: longer, more intense wildfire seasons; more droughts; insects that survive milder winters; and tree species whose best climate zone is moving north faster than trees can spread (trees move only a few hundred metres per generation through seeds).
  • Wetlands and peatlands: drying can turn peatlands from carbon sinks into carbon sources.
  • Species shifts: southern species moving north (for example, blacklegged ticks), while northern species such as moose face more heat stress and parasites (winter ticks) along the southern edge of their range.
  • Seasonal timing: earlier springs can cause mismatches between when food is available and when animals need it. Maple syrup producers see the sap season shifting with warmer winters.

Impacts on ecosystems around the world

  • Arctic: shrinking sea ice, thawing permafrost, and tundra turning greener as shrubs spread north.
  • Coral reefs: marine heat waves cause coral bleaching (corals expel the algae that feed them); acidification makes it harder to build skeletons. Reefs support a huge share of ocean biodiversity.
  • Mountains: glaciers shrinking; species pushed uphill until there is no higher place to go.
  • Coasts: rising seas and storms flood salt marshes and mangroves that protect shorelines and nurse young fish.
  • Drylands and forests: longer droughts and bigger wildfires, which can shift forests to grasslands or shrublands.

Who is most vulnerable?

Species and ecosystems are most at risk when they:

  • have a narrow tolerance (for example, cold-water fish, corals);
  • can't move easily or have nowhere to go (mountaintop species, island species, species in small, isolated patches);
  • reproduce slowly (long-lived trees, large mammals);
  • depend on one key feature that is disappearing (sea ice for polar bears and seals);
  • are already stressed by other threats (habitat loss, pollution, invasive species).

This is why reducing the other HIPPO threats also helps ecosystems cope with climate change.

Initiatives for combatting climate change

Global

  • The Intergovernmental Panel on Climate Change (IPCC) assesses the science for governments.
  • The Paris Agreement (2015): countries agreed to keep warming well below 2 °C and pursue 1.5 °C, and each submits its own emissions targets, which are supposed to get stronger over time.

National (Canada)

  • The Canadian Net-Zero Emissions Accountability Act (2021) commits Canada to net-zero emissions by 2050; Canada's 2030 target set under the Act is 40 to 45% below 2005 levels (targets and plans are reviewed over time).
  • Federal and provincial programs aim to clean up electricity, make buildings more efficient, cut methane from the oil and gas industry, and expand zero-emission vehicles. (Specific programs change often; check current government websites.)

Provincial and local (Ontario)

  • Ontario phased out coal-fired electricity; its last coal plant stopped burning coal in 2014. This also improved air quality.
  • Many cities have climate plans; for example, Toronto's TransformTO aims for net-zero community emissions by 2040.
  • Conservation authorities, land trusts and community groups restore wetlands, plant trees and protect natural corridors, such as the effort to link Algonquin Park to the Adirondacks in New York State.

Individuals and schools: saving energy, choosing active transportation and transit, reducing food waste, planting native species, and speaking up in the community.

CLIMATE CHANGEcauses and impactsMITIGATIONreduce the CAUSEADAPTATIONcope with the IMPACTS• cut fossil fuel use• clean electricity, heat pumps• protect forests, wetlands, peat• cut methane from landfills, farms• wildlife corridors so species can move• restore wetlands to absorb floods• shade trees and cooling centres• heat- and drought-tolerant crops
The two kinds of climate solutions. Mitigation slows climate change; adaptation reduces the harm from changes that are already happening. Some actions, like restoring wetlands, do both.

Solutions that help ecosystems adapt

  • Connect habitats with corridors and eco-passages so species can shift their ranges.
  • Protect climate refuges: places that stay cooler or wetter, like deep, cold lakes and north-facing slopes.
  • Reduce other stresses (pollution, invasive species, overharvesting) so ecosystems are more resilient.
  • Nature-based solutions: restored wetlands store carbon and absorb floodwater; urban trees store carbon and shade streets.
  • Assisted migration (carefully planting tree species slightly north of their current range) is being studied and tested by foresters.
NORTH ↑ (cooler)SOUTH ↓ (warmer)protected area Aprotected area Bhabitat corridoras climate warms, speciesneed to shift north
Schematic (not a real map): a habitat corridor connects two protected areas so plants and animals can move north as their old range becomes too warm. Without a connection, species can get trapped in a shrinking patch of suitable climate.
Worked example

Let's assess an impact using evidence

Assess the impact of climate change on the sustainability of brook trout streams in southern Ontario. Use at least two indicators and one ecosystem concept.

  1. Indicator 1: rising summer air and water temperatures. Brook trout need cold water (they are stressed well before the water gets as warm as a typical swimming beach).
  2. Indicator 2: more intense rainstorms cause more erosion, which fills gravel spawning beds with sediment, and warm runoff from pavement heats streams further.
  3. Concept: dissolved oxygen. Warmer water holds less oxygen (Lesson 7), so trout get squeezed by heat and low oxygen.
  4. Concept: dynamic equilibrium. Cold-water species decline and warm-water species move in, shifting the stream to a new equilibrium.
  5. Judgement: streams fed by cold groundwater springs and shaded by trees are more likely to stay suitable (climate refuges).

Climate change reduces the sustainability of many brook trout streams, especially unshaded ones in urban and farm areas. Protecting groundwater, planting shade trees and reducing runoff can help.

Worked example

Let's evaluate solutions with criteria

A town has money for one project: (A) restore a 40-hectare wetland on the river; (B) build a concrete flood wall. Evaluate both for climate mitigation, adaptation, biodiversity and cost.

  1. Mitigation: A stores carbon in wetland soil and plants (yes). B: concrete production releases CO₂ (no, slightly negative).
  2. Adaptation: both reduce flooding. B protects one spot strongly; A stores floodwater across a wide area and slowly releases it, which also helps in droughts.
  3. Biodiversity: A creates habitat for fish, frogs, birds and plants. B removes riverbank habitat.
  4. Cost and time: B may protect sooner; A needs time to grow but costs less to maintain and gets better over time.
  5. Decision: A scores higher on most criteria, unless the town faces an urgent risk that only a wall can address quickly.

The wetland is a nature-based solution that helps with both mitigation and adaptation and increases biodiversity; the flood wall does adaptation only. Using criteria makes the decision clear and fair.

Hands-on activity

Climate action decision matrix (A2.4)

You need: paper or a spreadsheet, internet access with a grown-up's OK.

  1. Research one climate initiative in your own community, region or school (for example, a municipal climate plan, a tree-planting program, a transit project, a wetland restoration, or a school eco-team project). Write down: who runs it, what it does, and whether it is mitigation, adaptation or both.
  2. List four possible climate actions your household or school could take (for example: switching off and unplugging, walking or cycling to school, a waste-free lunch plan, planting native trees, a home energy check with a grown-up).
  3. Make a decision matrix: rows are the four actions; columns are criteria scored 1 (low) to 3 (high): emissions saved, cost (3 = cheapest), ease, benefit to ecosystems, how many people it involves.
  4. Add up the scores. Choose the top action and write a short plan: what, who, when, and how you will measure success.
  5. Reflect: what can individuals do, and what needs governments or businesses? Why are both needed?

What to look for: a clear table, honest scores with reasons, a realistic plan, and an understanding that big emissions cuts need system changes (clean electricity, transit, building codes) as well as personal actions.

Just for fun

Mitigation and adaptation walk into a very hot room. Mitigation turns down the heater. Adaptation puts on a T-shirt. The smartest person in the room does both.

Your turn

1

Describe two impacts of climate change on Ontario ecosystems.

2

Describe two global ecosystem impacts.

3

What is the difference between mitigation and adaptation? Give an example of each.

4

What did countries agree to in the Paris Agreement?

5

What are Canada's legislated climate targets?

6

Why are polar bears especially vulnerable to climate change?

7

Explain how a habitat corridor helps species adapt to climate change.

More practice: warm-up

1

What does net-zero emissions mean?

2

In what year did Ontario's last coal plant stop burning coal?

3

What is coral bleaching?

4

Give an example of a nature-based solution.

5

What does IPCC stand for?

More practice: on your own

1

Why might warm-water fish species benefit from climate change in Ontario lakes, and why is that still a concern?

2

Explain how drying peatlands could make climate change worse.

3

Why does reducing pollution and invasive species help ecosystems cope with climate change?

4

Classify each as mitigation, adaptation or both: (a) a green roof; (b) an electric bus; (c) a cooling centre during a heat wave; (d) restoring a forest.

5

Trees spread only a few hundred metres per generation. Why is this a problem as the climate warms?

Challenge

1

Assess this claim: "Climate change will be good for Canada because it will make our winters milder." Consider at least three ecosystem impacts in your answer.

2

Compare a global initiative and a local initiative for combatting climate change: what each can do that the other can't.

3

Design one adaptation strategy for a species at risk in Ontario facing climate change. Explain how it addresses vulnerability.

Check your understanding

Quiz

1.

Which is an example of MITIGATION?

2.

The Paris Agreement aims to keep warming...

3.

Canada's law commits it to net-zero emissions by...

4.

Which species is MOST vulnerable to climate change?

5.

Why do Hudson Bay polar bears struggle as the climate warms?

6.

Restoring a wetland that stores carbon and soaks up floodwater is...

7.

What is the main purpose of a habitat corridor in a warming climate?

For parents and teachers

Big idea (B1.1): climate change is reducing the sustainability of many local and global ecosystems, especially for species with narrow tolerances that can't move. Initiatives at every scale (Paris Agreement, Canada's net-zero law, Ontario's coal phase-out, city climate plans, conservation corridors, personal actions) work on mitigation, adaptation or both. Analysing how initiatives fit their social, economic and cultural context builds A2.3; evaluating solutions with criteria builds scientific literacy (A2.4).

How to help: Find your municipality's climate plan together. Do the decision matrix as a family and agree on one action to try for a month.

Common difficulties:

  • Mixing up mitigation and adaptation. Mitigation = fewer emissions (cause); adaptation = less harm (effect).
  • Thinking only individuals or only governments matter. Both are needed.
  • Climate worry. Emphasize that every tenth of a degree of avoided warming reduces harm, and that many solutions also bring other benefits (cleaner air, lower bills).

Sources: Paris Agreement (UNFCCC); Canadian Net-Zero Emissions Accountability Act (Government of Canada); Ontario coal phase-out completed 2014 (Government of Ontario); TransformTO net-zero 2040 (City of Toronto); Algonquin to Adirondacks Collaborative; Hudson Bay polar bears and sea ice (Environment and Climate Change Canada).