How do ecosystems change

-A 200-year-old tree shaded the forest floor throughout its life.- When it falls in a storm, the forest floor will receive much more sunlight.

Seedling that require a lot of sunlight will have a chance to grow.

Other plants that grow best in shade might not survive .

Ecosystem change

200-year-old tree shaded the forest floor.

200-year-old tree falls in a storm.

The forest floor receives much more sunlight.

The change may affect animals too. Birds that nested in the tree may need to find new home.

but the fallen tree may provide habitat for salamanders and other animals .

The change affects birds to find new home.

Fallen tree provides habitat for salamanders.

Living things cause change

People cut down trees to build homes. -They clear land in order to grow food in open fields. People are living things that cause change in their

environment .

The groundhogs live underground in tunnels, or burrows.As they dig their burrows, they change the environment.

-These changes can be harmful. Groundhogs can damage crops, lawns, and the roots of

the trees .

-Some living things benefit from changes that groundhogs cause. -Foxes, rabbits, and other animals live in burrows made by groundhogs.

-Groundhogs improve soil by mixing it as they dig.-This benefits plants that grow in the soil.

-Fires can burn forests.-Hurricanes can wash away beaches and knock down trees. They can cause floods.

Natural Events Cause Change

Floods change ecosystems too.They kill plants and destroy animal habitats.

Droughts can change ecosystems.During drought, very little rain falls.Plants die from lack of water.

If animals cannot find enough water, then they may die or move to other places.

drought

Not all living things are harmed by changes to ecosystems. A forest fire may destroy trees and animals'

homes.1- But the fire also clears dead plants and wood from the forest floor. Then trees have more space to grow. 2- Plants that need more sunlight can also grow. Ash from the fire makes soil healthy. Ash contains minerals that plants need

Plants grow in an area cleared by fire.

Seasonal change

In some ecosystems, the cycle of the seasons brings major changes.

- Summers may be warm, but winters may be very cold and snowy.- Some plants die in winter.- Food may be hard to find for

some animals .

A dead plant in winter

Many plants and animals have adaptations that help them survive these changes.

Adaptation is a trait that helps a living thing survive in its environment.

Trees shed their leaves before winter. This reduces the amount of water

they need to take in during winter .

Some trees shed their leaves in winter. When spring comes, new leaves will grow.

The shedding leaves

Some animals, such as bats and ground squirrels, hibernate, or sleep, through the winter.

hibernating ground squirrel

Hibernating bats

Golden plover travels more than a thousand miles when it

migrates.

The volcano Mount St. Helens erupted in the state of Washington. This eruption was huge. The blast changed the

ecosystem .

Living things Return

1 -It knocked over trees.2- It burned whole forests and killed many animals.3- Rivers of mud covered large areas.4-The volcano released a cloud of ash into the air.5- Winds carried the ash around the world.

Rivers of mud covered large areas.

A cloud of ash is released into the air.

over time, however, wind carried the seeds of grasses, flowers, and trees to the mountain. new plants began to

grow .

Spiders and beetles arrived. Birds returned to live in the standing dead trees. Small and large mammals also returned.

Each new change allowed more kinds of plants and animals to live there again.The ecosystem is not the same as it was before the eruption. But it is covering.

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