Unit A Lesson A10 Ecosystem Destruction and Renewal
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Lesson A10: Ecosystem Destruction and Renewal
Video Lesson
Nature has ways of renewing itself. When ecosystems are damaged or destroyed, renewal begins.. Watch this video to learn how ecosystems renew themselves.
Lesson A10: Ecosystem Destruction and Renewal
Ecosystems Change
Ecosystem change often is so gradual we cannot even notice it, occurring over years or centuries.
Ecosystem change often is so gradual we cannot even notice it, occurring over years or centuries.
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Abiotic factors can cause ecosystems to change. Warmer winters allow a new tree species to spread slowly into a forest ecosystem.
- The organisms themselves cause change. A forest of trees eventually re-grows on abandoned farm land. Seeds carried by birds and on winds sprout in the sunny soil. Animals move in and out as food webs grow more complex.
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 62–63
Materials:
No other materials are needed for this lesson.
Figure A.3.10.1 – Natural areas like Waterton National park are excellent locations to study ecosystems and succession.
Figure A.3.10.2 – The ecosystem on this abandoned farmstead is beginning to change.
Figure A.3.10.3 – Bushes like buffalo berry and wild rose are the first large plants to grow on the old farm.
Succession
The process of ecosystem change is called succession. On abandoned Alberta farmland, sun-loving fast-growing grasses and herbs appear first. If the area was naturally grassland, this might be where the succession process ends. If not, dense shrubs such as buffalo berry, wild rose, and highbush cranberry show up next. A decade later, small trees such as aspen and poplar dot the land.
The process of ecosystem change is called succession. On abandoned Alberta farmland, sun-loving fast-growing grasses and herbs appear first. If the area was naturally grassland, this might be where the succession process ends. If not, dense shrubs such as buffalo berry, wild rose, and highbush cranberry show up next. A decade later, small trees such as aspen and poplar dot the land.
Their lightweight seeds blow on the wind and sprout on the open soil. The diversity of organisms increases, and the whole ecosystem grows more diverse and complex.
During this process, food chains are changing from simple chains into complicated webs. Decades later, slower-growing white spruce take root and grow. They colonize and shade out other trees and shrubs. Only a small amount of brief sunlight reaches the forest floor. The ecosystem is maturing. This is a climax ecosystem.
Suddenly everything changes! A fire rages. The ecosystem is damaged. Habitats are destroyed. However, the ingredients for life are still here. The soil is almost untouched. Some trees are still alive. They are charred, but they will soon sprout new needles. Sunlight now reaches the forest floor. Nutrients are recycled. New species now have opportunity to move in. The ecosystem not only will recover from the fire, it will be renewed.
During this process, food chains are changing from simple chains into complicated webs. Decades later, slower-growing white spruce take root and grow. They colonize and shade out other trees and shrubs. Only a small amount of brief sunlight reaches the forest floor. The ecosystem is maturing. This is a climax ecosystem.
Suddenly everything changes! A fire rages. The ecosystem is damaged. Habitats are destroyed. However, the ingredients for life are still here. The soil is almost untouched. Some trees are still alive. They are charred, but they will soon sprout new needles. Sunlight now reaches the forest floor. Nutrients are recycled. New species now have opportunity to move in. The ecosystem not only will recover from the fire, it will be renewed.
Figure A.3.10.4 – Aspens and poplars grow on the abandoned farmland.
Figure A.3.10.5 – Eventually, the farmland matures into a white spruce forest.
Figure A.3.10.6 – A forest fire damages the ecosystem. It is a trigger for change.
Figure A.3.10.7 – Two photos of the same place in a boreal forest: the one on the left is taken one year before a forest fire and the one on the right is taken two years after the fire.
What Drives Succession?
These before and after photos (Fig A.3.10.7) show secondary succession. A forest fire has disturbed the ecosystem. Afterward, new plants begin to cover the forest floor. Nutrients from the charred debris and plenty of sunlight produce good growing conditions. This process of succession follows a predictable pattern. Fire, windstorms, floods, and severe drought all bring opportunities for change.
Logging, a man-made disturbance, can be an agent for succession when done in an ecologically sensitive way. Clearcut logging, in which all vegetation is removed, often leads to soil erosion. When soil is damaged or removed, secondary succession has no place to begin. The ecosystem can be damaged permanently. Selective logging, where only the oldest trees are removed, brings sunlight into the forest. With selective logging, the soil remains intact, and a wide variety of organisms can move in immediately.
These before and after photos (Fig A.3.10.7) show secondary succession. A forest fire has disturbed the ecosystem. Afterward, new plants begin to cover the forest floor. Nutrients from the charred debris and plenty of sunlight produce good growing conditions. This process of succession follows a predictable pattern. Fire, windstorms, floods, and severe drought all bring opportunities for change.
Logging, a man-made disturbance, can be an agent for succession when done in an ecologically sensitive way. Clearcut logging, in which all vegetation is removed, often leads to soil erosion. When soil is damaged or removed, secondary succession has no place to begin. The ecosystem can be damaged permanently. Selective logging, where only the oldest trees are removed, brings sunlight into the forest. With selective logging, the soil remains intact, and a wide variety of organisms can move in immediately.
Figure A.3.10.8 – A machine removes the limbs from a spruce tree that was just cut down.
What drives succession? Why do ecosystems change and mature? Change is driven ultimately by the species that inhabit an area. They change the sunlight conditions. They change the soil. Animals move in and they disperse new seeds into the area. Insects
arrive to pollinate flowering trees, shrubs, and smaller plants.
After a fire, new plants grow on the forest floor. They produce conditions favourable for shrubs and fast-growing trees. Those species make conditions where slow-growing larger trees can take root.
After a fire, new plants grow on the forest floor. They produce conditions favourable for shrubs and fast-growing trees. Those species make conditions where slow-growing larger trees can take root.
Figure A.3.10.9 – Southern Alberta has many badlands that show a slow process of succession.
Figure A.3.10.10 – Succession happens in and around water as well.
Succession Happens Everywhere
Succession is not limited to forests. It occurs in all ecosystems, including deserts, ocean, and shorelines of lakes. Each succession pattern is unique to the location. However, every location follows a predictable pattern. This predictable pattern was noticed in the late 1800s. Ecologists use these patterns to predict changes in ecosystems after disturbances.
Ecosystems mature only so far. Eventually, they evolve into stable self-perpetuating climax communities. The ecosystem reaches equilibrium. It changes slowly as climate and other factors change. Eventually, an event disturbs it. When this occurs, the succession engine will turn on again. The quicker pace of succession brings renewal.
Life Reboots on a Rock
Succession is not limited to forests. It occurs in all ecosystems, including deserts, ocean, and shorelines of lakes. Each succession pattern is unique to the location. However, every location follows a predictable pattern. This predictable pattern was noticed in the late 1800s. Ecologists use these patterns to predict changes in ecosystems after disturbances.
Ecosystems mature only so far. Eventually, they evolve into stable self-perpetuating climax communities. The ecosystem reaches equilibrium. It changes slowly as climate and other factors change. Eventually, an event disturbs it. When this occurs, the succession engine will turn on again. The quicker pace of succession brings renewal.
Life Reboots on a Rock
Figure A.3.10.11 – A scientist is monitors insect populations in this ecosystem.
Much of the northern hemisphere, including all of Canada, was covered in a thick sheet of ice 25 000 years ago. The ice was not stationary. It advanced and retreated as temperatures went up and down. As glaciers moved, they ground away the land as if
they were gigantic scouring brushes. Animals that could not move to warmer locations died. Mastodons, giant beavers, small horses, camels, and huge sloths all died out. Modern animals we know today such as caribou, wolves, and moose survived.
Figure A.3.10.12 – During the last ice age Canada was covered completely in ice sheets more than 1 km thick. Image by
Hannes Grobe.
All plant life was crushed and ground away under the thick ice. Rock was ground into pebbles. Soil was washed away in melt-water floods. The entire living ecosystem was removed. However, what was the landscape like immediately after the ice retreated?
This was as close to the lifeless surface of the Moon as Earth gets. Only breathable air, water, and livable temperatures allowed new life to start again.
Primary Succession
What can live in an area that is covered only in rock? There is no soil. The foundation of any land-based ecosystem is missing. Luckily, a few plants can manage under these barren conditions. They arrive as spores carried on winds from far away. These tough organisms are called pioneer species. They make way for other organisms to repopulate areas that are completely barren.
This was as close to the lifeless surface of the Moon as Earth gets. Only breathable air, water, and livable temperatures allowed new life to start again.
Primary Succession
What can live in an area that is covered only in rock? There is no soil. The foundation of any land-based ecosystem is missing. Luckily, a few plants can manage under these barren conditions. They arrive as spores carried on winds from far away. These tough organisms are called pioneer species. They make way for other organisms to repopulate areas that are completely barren.
Figure A.3.10.13 – What could live here? Lichens can colonize bare rock.
For example, lichen can live on bare rock. Lichen is actually two species living together in a mutualistic symbiotic relationship. The blue-green algae make food from sunlight, and the fungi absorb minerals from the rock. They often are the first and
only organisms to live in barren areas. For a while, the lichen represent one of the simplest self-contained ecosystems possible.
The lichen slowly break down rock into soil. Blown-in moss spores soon grow in the thin soil, too. Lichens and moss decay, contributing plant matter. Microbes can begin to work on nutrient recycling. They also blow in as tough coated spores. Seeds of grasses and ferns blow in and take root in the thickening soil. Insects arrive on the winds. Birds fly in to nest in new predator-free areas. Eventually, shrubs and trees sprout, followed by larger animals. The ecosystem changes and grows into the complex ecosystem we enjoy today. But all this takes time!
The lichen slowly break down rock into soil. Blown-in moss spores soon grow in the thin soil, too. Lichens and moss decay, contributing plant matter. Microbes can begin to work on nutrient recycling. They also blow in as tough coated spores. Seeds of grasses and ferns blow in and take root in the thickening soil. Insects arrive on the winds. Birds fly in to nest in new predator-free areas. Eventually, shrubs and trees sprout, followed by larger animals. The ecosystem changes and grows into the complex ecosystem we enjoy today. But all this takes time!
Glaciation, volcanic eruptions, and plate tectonics result in areas where all life is wiped away. Tough pioneer species move in to build the foundations for new ecosystems. Primary succession offers a glimpse into how life started on Earth. Life on Earth
began as a kind of primary succession process.
Watch More
How Fire Can Restore a Forest
Succession is a long and gradual process. Because succession happens slowly, appreciating how drastic the changes are is difficult. Watch a longleaf pine forest preserve change over just two months after fire ripped through. What kind of succession is this?
Succession is a long and gradual process. Because succession happens slowly, appreciating how drastic the changes are is difficult. Watch a longleaf pine forest preserve change over just two months after fire ripped through. What kind of succession is this?
Life After Lava
Often, an important ecological step is simply to leave things alone. After a major disturbance, such as a volcanic eruption or a forest fire, people want to help Mother Nature. The exposed land looks barren. By moving in and planting trees, for example, we often do more harm than good. We can produce a very uniform new forest, but it lacks biodiversity. The forest did not go through all the early stages of succession. Those stages are critical to establishing the diversity that a healthy ecosystem needs. Learn more in this video called “Life after Lava”.
Often, an important ecological step is simply to leave things alone. After a major disturbance, such as a volcanic eruption or a forest fire, people want to help Mother Nature. The exposed land looks barren. By moving in and planting trees, for example, we often do more harm than good. We can produce a very uniform new forest, but it lacks biodiversity. The forest did not go through all the early stages of succession. Those stages are critical to establishing the diversity that a healthy ecosystem needs. Learn more in this video called “Life after Lava”.
Figure A.3.10.14 – Healthy coral reefs have an amazing diversity of living things.
Figure A.3.10.15 – Reefs can become sick or be damaged by in the surrounding water.
Succession in Aquatic Ecosystems
Succession is not limited to ecosystems on land. It is a natural part of the coral reef ecosystem as well. Coral reefs face destruction from hurricanes and cyclones. Violent water currents crash against the delicate coral formations. The coral breaks apart and forms large dead drifts on the seafloor. Even dead coral provides shelter for many fish and other animals. After each storm, new coral grows and re-colonizes the reef. Nature maintains a balance between destruction and renewal in the reef ecosystem. That balance is being destroyed by human activity. The runoff of fertilizers into the ocean results in algae blooms. The algae consume almost all oxygen in the water.
Succession is not limited to ecosystems on land. It is a natural part of the coral reef ecosystem as well. Coral reefs face destruction from hurricanes and cyclones. Violent water currents crash against the delicate coral formations. The coral breaks apart and forms large dead drifts on the seafloor. Even dead coral provides shelter for many fish and other animals. After each storm, new coral grows and re-colonizes the reef. Nature maintains a balance between destruction and renewal in the reef ecosystem. That balance is being destroyed by human activity. The runoff of fertilizers into the ocean results in algae blooms. The algae consume almost all oxygen in the water.
Coral, fish, and other marine animals need oxygen to live, so they suffer. In addition, climate change is stressing coral reefs. Carbon dioxide from the burning of fossil fuels makes the oceans too acidic. Hurricanes and cyclones are more severe because
the air is warmer. Coral reefs around the world are dying.
Humans Helping Succession
Humans can affect succession in positive ways such as with dying coral reefs. Some people actually garden coral. Coral chunks are grown in tanks or protected areas of ocean. When they are large enough, the chunks are glued to dead reefs. With a head start, the coral begin to grow and re-colonize the reef. Fish and other reef animals move back quickly into the fresh reef. Usually, interfering in a natural succession process is unwise because negative consequences that we cannot see might occur. However, when ecosystems are in severe danger, sometimes human assistance can stop the complete loss of an ecosystem.
Humans Helping Succession
Humans can affect succession in positive ways such as with dying coral reefs. Some people actually garden coral. Coral chunks are grown in tanks or protected areas of ocean. When they are large enough, the chunks are glued to dead reefs. With a head start, the coral begin to grow and re-colonize the reef. Fish and other reef animals move back quickly into the fresh reef. Usually, interfering in a natural succession process is unwise because negative consequences that we cannot see might occur. However, when ecosystems are in severe danger, sometimes human assistance can stop the complete loss of an ecosystem.
Figure A.3.10.16 – Chunks of coral can be transplanted back to the ocean.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to
guide your learning.
Unit A Lesson 10 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
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REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
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Normally, letting nature take its course is best, but in some instances where ecosystem renewal may benefit from human assistance, humans can affect the process positively. A simple example is replanting of trees in an area that has burned or
where they have been cut.
Primary succession occurs in areas that are completely free of living organisms. This means that not even soil exists because no soil organisms are present. Few organisms can live on bare rock. They must extract minerals from the rock and catch
water from rain or mist. Lots of sunlight is available because no plant life produces shade. Lichens can live in these conditions. By living on rock, the lichen eventually produce a thin soil in which- other tough plants such as moss can live.
Eventually, many kinds of plants and animals can live in the area.
Primary succession is a process that starts in an area with no living organisms. Secondary succession begins in an ecosystem that is disturbed but some organisms are present. Both types of succession occur after areas are disturbed. Primary
succession occurs after catastrophic events such as volcanic eruptions and glaciation. Secondary succession occurs after forest fires, floods, droughts, and man-made disturbances such as logging and farming. Both types of succession follow
predictable patterns of change unique to the area.
Succession ends with a climax community, which is is a community that has reached a steady state, or equilibrium, with its environment. This is an ecosystem that contains organisms and relationships that are best suited to the abiotic conditions.
The rate of change slows but it does not stop. Climax communities continue to change slowly as climate and geology change.
In Canada's boreal forest, summers are short and cool. This means that the decay of dead logs and other plant material is slow. Plant debris (sometimes called duff) accumulates on the forest floor. Fire reduces this material to nutrient-rich
ash. It also opens the forest, allowing sunlight to reach the soil and warm it. These ideal conditions stimulate new growth from seeds and roots.