⏳ Estimated Reading Time: 8 - 10 minutes

Explain how natural disruptions, both short- and long-term, impact an ecosystem.

Disruptions to Ecosystems

Natural disruptions are events that alter the structure, function, or composition of an ecosystem. Disruptions can be caused by natural factors, such as climate change, natural disasters, and invasive species, or by human factors, such as land use change, overexploitation, pollution, and urbanization. In this lesson, we will focus primarily on natural disruptions to ecosystems.

Natural disruptions can have both short- and long-term impacts on an ecosystem, depending on the type, frequency, intensity, duration, and scale of the disruption.

Essential Knowledge

Natural disruptions to ecosystems have environmental consequences that may, for a given occurrence, be as great as, or greater than, many human-made disruptions.

Short-Term Disruptions

***A forest fire can clear vegetation, resetting succession, and creating opportunities for new species to colonize.***

Short-term disruptions, such as storms, wildfires, or seasonal variations, can lead to immediate changes in ecosystem dynamics.

The short-term negative effects of a forest fire could be the destruction of habitats and a reduction in biodiversity, but the long-term positive effects, such as increasing the availability of nutrients and opportunity for regeneration often outweigh the negative effects in ecosystems adapted to periodic disruption by fire.

Short-term disruptions may also affect populations of organisms, leading to shifts in abundance and distribution. Some of the short-term impacts of natural disruptions on an ecosystem are:

Loss of biomass, productivity, and diversity of organisms
Change in the distribution, abundance, and behavior of organisms
Alteration of the physical and chemical properties of the environment
Disruption of the ecological processes and services, such as nutrient cycling, water purification, and pollination

Everglades Case Study

The Everglades of Florida cover about 18,000 square miles and are adapted to periodic flooding, which helps to recharge the aquifer, enhance water quality, sequester carbon, and provide habitats for wildlife. Many threatened or endangered species call the Everglades homes, such as the Florida panther, American crocodile, and the wood stork. The Everglades also provide many ecosystem services to humans, such as fresh water (provisioning), flood control (regulating), recreation (cultural), and tourism (cultural).

The Everglades is threatened by human activities and infrastructure, resulting in the loss of wetland area, the degradation of habitat, and the decline of wildlife populations. Natural floods, however, can cost hundreds of thousands of dollars in lost infrastructure and human life. Over time, we have altered the natural flow of water to the Everglades to reduce damage to human infrastructure by flooding.

Three side-by-side maps of Florida depict water flow: ‘Historic Flow’ on the left, ‘Current Flow’ in the middle, and ‘CERP Planned Flow’ on the right, color-coded to illustrate changes and restoration efforts in the Everglades. — ***The CERP aims to restore the natural flow and function of the Everglades ecosystem and is expected to take 50 years to complete.***

However, we have learned that the disruption in ecosystem services provided by the Everglades has been costly in terms of water supply and flood protection. In 2000 Congress authorized the largest and most comprehensive environmental restoration plan in United States history, known as the Comprehensive Everglades Restoration Project (CERP).

The CERP seeks to balance the water-related needs of the region, such as water supply and flood protection, with the ecological needs of the natural system. By restoring the natural flow and function of the Everglades, the CERP can enhance the ecosystem services, such as water purification, carbon storage, and habitat provision, that support the human well-being and the environmental health of South Florida.

Long-Term Disruptions

Long-term disruptions can result from processes like climate change, geological events, or changes in sea level. For example, geological events like volcanic eruptions or tectonic activity can reshape landscapes, creating new features and altering soil composition.

Some of the long-term impacts of natural disruptions on an ecosystem are:

Recovery, adaptation, or extinction of organisms
Succession, evolution, or speciation of organisms
Transformation, resilience, or collapse of the ecosystem
Restoration, conservation, or enhancement of the ecosystem services

Earth system processes have different impacts on the Earth’s environment and life, depending on their scale and type. They are the natural phenomena that shape and regulate Earth’s environment, such as plate tectonics, climate, weather, and biogeochemical cycles. These processes operate on a range of scales in terms of time, meaning that they can occur at different frequencies and durations.

An infographic with three columns explains ‘Periodic,’ ‘Episodic,’ and ‘Random’ processes, using examples like tides and meteorites, against a predictability scale from high to low. — Processes can be periodic, episodic, or random, depending on how regular or predictable they are. The graphic includes some examples of periodic, episodic, and random processes and the degree of predictability of each.

Some processes can cause gradual and continuous changes, such as the evolution of species and the formation of continents. Some processes can cause sudden and dramatic changes, such as the extinction of species and the alteration of climate. Some processes can cause both types of changes, depending on the context and perspective. In general, periodic processes can be forecasted with high accuracy, episodic processes are modeled with some uncertainty, and random processes are just that, random, with little to no predictability.

Explore the tabs below to learn about two long-term disruptions: climate change and sea level change. Which do you think would have the most wide-ranging consequences?

Climate Change
Sea Level Change

Climate Change

Earth’s climate has changed over geological time, which is the span of millions or billions of years, for many reasons. Explore the cards below to learn more about how natural events can change the Earth's climate:

Rising global temperatures can be a positive feedback loop that accelerates climate change.

An infographic illustrates the relationship between global temperatures, glacial melting, reflectivity (albedo), and solar radiation absorption. Four circles connect with arrows: ‘Increasing Global Temperatures,’ ‘Glacial/Ice Melting,’ ‘Decreasing Albedo,’ and ‘Solar Radiation Absorption.’ — ***A warmer climate can melt ice and snow, which can reduce the albedo (reflectivity) of the Earth’s surface, which can absorb more solar radiation, which can further warm the climate.***

Earth’s climate is not static, but dynamic and variable. It has experienced many cycles of warming and cooling, as well as periods of stability and instability, over geological time. These changes have affected the environment and life on Earth, and have left traces in the geological record, such as fossils, ice cores, and tree rings, that can be used to reconstruct past climate.

If you just look at JUST the last 65 million years, it looks like Earth's temperature has continually DECREASED:

A line graph depicts the decline in global surface temperatures over the past 65 million years, with a sharp decrease recently, compared to the 1850-1900 average, illustrating long-term climate change. A graph of how global temperatures have changed over the last 65 million years.

However, if you look at a longer time scale, 500 million years, you can see the cyclical nature of Earth's temperatures:

a graph titled ‘Estimated global temperature over the last 500 million years.’ It shows temperature fluctuations with peaks like ‘Cretaceous Hot’ and valleys indicating cooler periods. The graph highlights times with and without polar ice caps, reflecting significant climate variability. — Earth has been significantly hotter than it is now. Once average global temperatures get above a certain level (around 68^o F), there is NO ice at the poles, which means significantly less land is available as habitat for animals, plants, and humans due to rising sea levels.

Sea Level Change

Sea level is the height of the ocean surface relative to the land. Sea level changes over geological time (millions of years) because of two main factors: the shape of the ocean basins and the amount of glacial ice on land.

The shape of the ocean basins is affected by plate tectonics, which is the movement of the Earth’s crust. Plate tectonics can change the size, depth, and location of the ocean basins over time. This can also affect how much water the ocean can hold, and thus the sea level. For example, if the ocean basins become deeper or larger, the sea level will drop. If the ocean basins become shallower or smaller, the sea level will rise.

This map shows global sea level changes from 1993 to 2018. Colors range from blue (decrease in sea level) to orange (increase in sea level). White dots represent data points. The title is ‘Sea Level Change (1993-2018). — **The increase in sea level from the** **20-year** **period between 1998 and 2018. We are currently experiencing sea level increases on the order of centimeters.**

An image divided into four sections illustrates sea level rise’s impact on a coastal area. The top section represents present-day conditions, including a beach, road, buildings, and forest. Subsequent sections show increasing sea levels (0.5m, 1.0m, and 2.0m), progressively flooding the area. Adapted from a USGS image, it highlights the consequences of rising sea levels. — ***An estimation of what sea level rise would look like for Santa Barbara, California. At 2 meters, coastal dwellings are at significant risk.***

Glacial ice is frozen water that accumulates on land, such as in Antarctica and Greenland. When the Earth’s climate is colder, more water freezes into glacial ice, and less water remains in the ocean. This lowers the sea level. When the Earth’s climate is warmer, some of the glacial ice melts and returns to the ocean, raising the sea level. As our climate is currently experiencing a warming period, glacial ice is melting, raising sea levels.

But what happens if the sea level increases more?

Changes in sea level can flood coastal areas, impacting both terrestrial and marine ecosystems.

We have several places in the coastal United States that are at or below sea level (ex. New Orleans). These places are very vulnerable to sea level rise because they are already below sea level.

A U.S. map titled ‘National Assessment of Coastal Vulnerability to Sea-Level Rise’ color-codes the Atlantic, Pacific, and Gulf coasts by risk levels: high, moderate, and very high. — The relative risk of coastal vulnerability to sea level rise in the United States. Several areas in the northeast, the Gulf of Mexico, Florida, California, and Oregon are at a very high risk of flooding from sea level rise.

Essential Knowledge

Earth system processes operate on a range of scales in terms of time. Processes can be periodic, episodic, or random.

Earth's climate has changed over geological time for many reasons.

Sea levels have varied significantly as a result of changes in the amount of glacial ice on Earth over geological time.

Results of Disruptions

Ecosystems exhibit varying levels of resilience, or the ability to recover and adapt to disturbances. Some species may be more resilient to certain disruptions, while others may struggle to cope. If you remember our lesson on biodiversity, the higher the species richness and evenness of an area, the more resilient an ecosystem is to disruptions.

Disruptions can redefine interactions among species, and the overall biodiversity of an ecosystem can be affected. Human activities can exacerbate or mitigate the impacts of natural disruptions.

birds migrating at dusk — ***Birds flying south for the winter is considered short term migration.***

Migration is the movement of animals from one location to another, usually in response to changes in the environment or the availability of resources. Migration can be short-term or long-term, depending on the duration and distance of the movement.

Short-term migration is usually seasonal, such as salmon swimming upstream to spawn.

Long-term migration is usually permanent, such as whales moving to different oceans or humans colonizing new lands.

Migration can be influenced by a variety of factors, including natural disruptions. These events can affect the habitat, food, water, or predators of wildlife, and cause them to migrate to find more suitable conditions. For example, some animals may migrate to escape a wildfire or a drought, while others may migrate to take advantage of the new resources or opportunities created by the disturbance. Wildlife migration is an important ecological process that affects biodiversity, population dynamics, and ecosystem functioning.

Essential Knowledge

Major environmental change or upheaval commonly results in large swathes of habitat changes.

Wildlife engages in both short- and long-term migration for a variety of reasons, including natural disruptions.

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