# Ecological Disturbances - How Ecosystems Are Disrupted **Channel:** Miacademy & MiaPrep Learning Channel **Source:** https://www.youtube.com/watch?v=cupWz8BpieA **Transcript page:** https://www.withtranscript.ai/video/cupWz8BpieA ## Chapters - 0:00 — Introduction to Ecological Stability - 1:54 — Factors That Stabilize Ecosystems - 3:37 — How Disturbances Change Ecosystems - 5:48 — Ecological Succession After Disturbance - 8:29 — Lesson Recap and Closing Remarks ## Transcript **[0:00]:** I want you to think about a place you are very familiar with that has changed over the years. It could be a park you visited frequently or maybe a restaurant or a part of a city you really enjoy. What was it like when you first went there and how is it different now? Places and communities change over time whether we want them to or not and the natural environment is no different. In today's lesson, we'll be exploring this concept as we describe the factors that affect ecological stability, explain how ecological disturbances affect ecosystems, and differentiate between the two kinds of ecological succession. Let's get into it. **[0:54]:** So far in this unit, we've learned how ecosystems are built from communities of living things and their environment, as well as the many ways that organisms interact with each other. Ecosystems are large and complex and everything within them is interconnected. Because of this, it can be helpful to think of an ecosystem as a giant superorganism. All of its parts rely on each other to survive. If one part of an ecosystem changes, it can affect every living thing within it. The question then becomes, how stable are ecosystems and what factors affect their stability? Ecological stability refers to an ecosystem's capacity to maintain roughly the same populations and conditions over time. In other words, a stable ecosystem is one that doesn't change much or rebounds quickly when changes do occur. You can think of this in the same way as homeostasis or balance in an individual organism. **[1:54]:** Let's start by identifying what factors help stabilize an ecosystem. Generally speaking, more biodiversity, or diversity of life, makes an ecosystem more stable. This is because different species take on different roles, providing support in a variety of conditions. Additionally, ecosystems are stabilized by the presence of keystone species, which are species within ecosystems that other species largely depend on. You can think of them as the glue that holds an ecosystem together. For example, beavers in wetland ecosystems build dams that block rivers and streams, physically creating environments that their neighbors need to survive. However, there is no such thing as a perfectly stable ecosystem. All ecosystems are subject to disturbances. A disturbance is an event that changes an ecosystem by impacting the amount of organisms or resources. What do you think are some disturbances that affect the stability of ecosystems? Write your thoughts in your guided notes. Some examples of disturbances are natural disasters, such as storms, floods, fires, and droughts, which can drastically change the landscape and availability of resources. **[3:09]:** Additionally, the dispersal of species can disturb ecosystems. Dispersal is when one or more individuals within a population move into a new area. This can affect the ecosystem these individuals leave and the ecosystem they move into, changing the balance of life in both. Finally, human activities, such as commercial fishing and clearing forests to create farmland, cause a large amount of disturbance in Earth's ecosystems. **[3:37]:** So, now that we know what disturbances are, how do they actually affect the overall stability of an ecosystem? Well, minor disturbances are common and, in a lot of cases, they are actually essential to maintaining healthy ecosystems. Disturbances create variable conditions, such as seasonal floods and drying periods, that benefit different species at different times. This provides opportunities for a variety of living things to succeed, increasing diversity. Disturbances can also help to renew ecosystems. For example, natural forest fires are relatively common in Yellowstone National Park, where local species have adapted to this disruption. The seeds of native lodgepole pine trees only sprout when exposed to extreme heat, using the burned forest as nutrition to grow. In this way, disruption can free up resources to rebuild old or dying parts of an ecosystem. So, disturbances are good for stability? Yes and no. As with all things, there is a balancing act. **[4:41]:** Not enough disturbance and ecosystems become too rigid, reducing opportunities and decreasing stability. Similarly, too much disturbance, like an incredibly large fire or terrible drought, can remove too many species or resources from an ecosystem too quickly, weakening its stability or in some cases destroying it completely. Most ecosystems are equipped to rebound from natural disasters, but some of the largest threats to their survival are human activity and invasive species. An invasive species is an organism that is introduced to a new environment and causes harm to the ecosystem. In many cases, humans knowingly or unknowingly play a part in this. For example, the zebra mussel is an invasive species native to Russia and Ukraine that has arrived in North America by attaching itself to boats. Upon arrival, these mussels outcompete local marine life and severely disrupt entire ecosystems. Other invasive species, such as lionfish, are introduced to new ecosystems when released into the wild by pet owners. **[5:48]:** The bottom line is disruptions happen for a variety of reasons and they inevitably cause change. In some cases, ecosystems change a lot. For example, if a terrible fire burns away most of the life within an ecosystem, what then? Well, the result is something called ecological succession, which is the process by which a community of living things rebuilds itself over time alongside its environment. To rebuild, ecosystems need soil, which is full of microscopic life and nutrients. Secondary succession occurs when a severe disturbance clears an existing community, but leaves soil intact. Wind and water carry life-bringing spores and seeds from neighboring ecosystems, which take root and sprout new plants over time. These plants support the arrival of new insects and animals, building a new community of life. Some common examples of disturbances that can cause secondary successions are fires, floods, storms, and human activity. On the other hand, primary succession occurs in an area where soil and life have not yet formed. **[6:59]:** This typically happens when new land is created by volcanic activity, or when a glacier melts, revealing land that was previously encased in ice. Similar to the process of secondary succession, wind and water play a vital role, delivering fertile soil so that plants can eventually begin to grow. Entire ecosystems have been built from scratch as a result of this very process, which is pretty incredible to think about. As the old saying goes, life uh finds a way. And with that, we have wrapped up our lesson on ecological disturbances. We've learned that ecological stability refers to an ecosystem's ability to maintain similar conditions over time. Stability is strengthened by increasing diversity of life and keystone species. A disturbance is an event such as a wildfire or human activity that changes an ecosystem by impacting the amount of organisms or resources. Minor disturbances help maintain healthy ecosystems by increasing diversity and renewing resources, while severe disturbances weaken stability by creating too much change too quickly. **[8:12]:** When ecosystems are forced to rebuild after a disaster, it's called ecological succession. Secondary succession occurs when some life is still present. And primary succession occurs in areas where soil and life have not yet formed. **[8:29]:** In our next lesson, we'll wrap up our unit on ecology as we explore the impact of human activity on ecological sustainability. Until then, fellow biologists, I'm Anthony, and remember life is full of wonders. So, keep learning and don't ever stop wondering. Hey! **[8:51]:** Hey! **[8:55]:** Hey! **[9:00]:** Hey!