Disruptions

0:00- [Narrator] Imagine this. You're walking through the Boreal Forest in North America, one of the largest forests on Earth, covering over two million square miles. Trees as far as the eye can see. (birds chirping) The air is cold and crispier. A light wind moves through the evergreen trees, mostly spruce, pine, fir, and larch.

0:27But then you see something strange. You walk into a massive clearing. Hundreds of trees have fallen over with their roots sticking out of the ground. Other trees are snapped in half like toothpicks. What happened here? These trees were damaged by what scientists call windthrow.

0:46This happens when really strong winds during a storm uproot or break trees. Windthrow is a powerful event that affects the biotic, or living, and abiotic, or non-living, parts of the ecosystem. We call this kind of event a disruption. In particular, windthrow is an example of a natural disruption, which is an event that happens all on its own without being caused by people.

1:12Other natural disruptions include droughts, earthquakes, floods, hurricanes, volcanic eruptions, tsunamis, and wildfires, unless we cause them, of course. These events can change ecosystems in lots of different ways. For example, droughts can dry up ponds and rivers, making it harder for plants to grow and animals to find water.

1:35Tsunamis bring huge waves that wash away soil and damage coastal habitats. Some disruptions though are caused by people, which we call human-caused disruptions. Examples of these include climate change, overfishing, and pollution. Let's think back to the boreal forest.

1:55People use wood from boreal forest trees to make all kinds of things like buildings, homes, and furniture. Because of this, forests are often carefully managed for logging, where trees are harvested or cut down, but then replanted. But in some cases, deforestation happens.

2:15Large areas of forest are cleared and trees aren't replanted. When people cause deforestation, habitats that many species depend on are destroyed. And without tree roots to hold soil in place, heavy rain can wash it away. This makes it harder for new plants to grow and changes how water moves through the environment.

2:39Disruptions can be small, like a single tree falling during a storm, or much larger, like hundreds of trees knocked down by a windthrow. We call this scale. Disruptions can range from small localized events to major global ones. Disruptions can also vary in how often they happen.

3:00Some disruptions are random, like a meteorite impact or an unexpected volcanic eruption. Others are much more predictable, like the start of hurricane season, and some are regular and frequent, like the changes in seasons or the rising and falling of tides every day in coastal areas.

3:18Even though they happen regularly, seasons and tides are considered disruptions because they can still cause predictable changes in the environment that organisms have to adjust to. Now, let's think about how disruptions can affect ecosystems. Some impacts to ecosystems happen quickly.

3:36This could include the immediate destruction of habitats or a drop in biodiversity or animals being forced to leave an area after a disruption. But some effects happen over a longer period of time. Depending on how severe or intense a disruption is, some species may be able to survive the changes that occur while others may face extinction.

4:01One way to understand these effects is by looking at how a disruption changes the flow of energy in a food web. So let's go back to the windthrow example in the boreal forest. In this ecosystem, the white spruce, a tree, and grasses are the main primary producers.

4:18They provide food for primary consumers, which include insects, birds, snowshoe hares, and squirrels. These organisms are then eaten by secondary consumers or predators, including coyotes, lynx, and raptors, like owls and hawks. If lots of white spruce trees are damaged or die, that means primary consumers have less food and fewer places to live.

4:43So their populations may start to decline. And if there are fewer of these organisms, the predators that rely on them also have less prey and less energy available. This means that the populations of predators will also decline. So one disruption can cause ripple effects throughout the food web, changing how energy flows through the entire ecosystem.

5:09So the next time you notice a disruption, whether it's big or small, think about how it might affect the whole ecosystem. A disruption can change where organisms live, what they eat, and how energy moves through the food web and in ways we don't always see at first.