Invasive species can greatly affect the natural balance in ecosystems. They change how living things interact with each other and with their environment. This can lead to serious problems for native species and the overall health of these ecosystems.

Competition
Invasive species often compete with native species for things like food, space, and nutrients. They can be more aggressive and reproduce faster, causing native species to disappear. For example, the zebra mussel, which was brought to North America, has taken over food and habitats from local freshwater mussels, hurting their populations.

Predation
Some invasive species become new predators in their new homes. Native animals might not be ready for these new threats. In Guam, the brown tree snake was introduced and led to the decline of many bird species. These birds hadn’t evolved to deal with this predator, which caused some of them to go extinct.

Hybrids and Genetic Pollution
Invasive species can mate with native species, creating hybrids. This mixing can weaken the unique traits that native species developed over time. For instance, non-native plants that interbreed with local plants can make it harder for native ecosystems to thrive.

Alteration of Habitat
Invasive species can change their new environments in harmful ways. A plant called Phragmites australis has taken over wetlands by outcompeting local plants. This change can destroy habitats and reduce the variety of living things in those areas.

Disease Vectors
Some invasive species can spread diseases that local species cannot fight off. For example, the fungal disease chytridiomycosis, brought by invasive frogs, has wiped out many frog populations around the world. Such diseases can have a big impact on whole ecosystems.

Trophic Cascades
When invasive species are introduced, it can cause a chain reaction in the food web. For example, if an invasive herbivore eats a lot of local plants, this can mean less food for plant-eating animals. This, in turn, can affect the predators that rely on those plant-eaters for food. These connections show how delicate ecosystems are.

Resource Availability
Invasive species can change how resources are available. They might alter soil chemistry or nutrient levels, which can hurt the growth of native plants. This ultimately affects animals that rely on those plants, impacting the entire food chain.

Abiotic Factors Shift
Invasive species can also impact physical factors like sunlight, soil, and water. Some invasive plants form thick mats in water, blocking sunlight essential for native underwater plants to grow. This can decrease plant variety and hurt the organisms that depend on them.

Ecosystem Services
The problems caused by invasive species can harm services that ecosystems provide. These include things like pollination, clean water, and carbon storage which are essential for human life. As native species decline, ecosystems struggle to provide these important services, affecting both our environment and economy.

Resilience and Adaptation
Invasive species can make an ecosystem less resilient. This means it can’t respond well to changes or recover from disasters like climate change. Healthy ecosystems usually have a lot of different species, which helps them bounce back, but invasive species can hurt this diversity, leading to weaker ecosystems.

In summary, invasive species have a big and complicated effect on native species and their interactions within ecosystems. They disrupt everything from competition and predation to the habitats and services that are vital for both nature and humans. Understanding these issues helps us come up with better strategies to protect native biodiversity and keep ecosystems healthy for the future.