Why Invasive Species Are a Problem


Invasive species are a threat to the environment. They can alter biodiversity and may also contribute to the destruction of entire ecosystems.


An invasive species is any living plant, animal, or parasite that is not normally part of an ecosystem.

what is an invasive species
  • Invasive species often spread very fast after invading a new ecosystem.
  • Their numbers can increase exponentially due to the lack of natural predators. This can greatly impact the population of the native species.
  • Invasive species can outcompete native species for space, food, and other resources in an ecosystem.
  • A species is invasive if it harms the plants and animals that normally live in an ecosystem. These species also adapt quickly to the new ecosystem they invaded.
  • Scientists also call invasive species alien species


A large percentage of invasive species get introduced into a new environment unintentionally. The means through which an invasive species is introduced into a new ecosystem is called a pathway.

How Invasive Species Spread

There are two types of routes: (Research from U.S. DEPARTMENT OF AGRICULTURE)

(i) Human Made Pathways

  • Many invasive species are spread by people. Basically, when people do different activities they can spread invasive species around. 
  • Sometimes spreading new species to new places happens by accident. For example, going boating in one lake and accidentally moving seaweed to another lake. Another example is when parasites or bugs get moved during international trade or flying.
  • Sometimes the new species is spread on purpose.  For example, bringing a new insect into an ecosystem to feed animals living there.  

(ii) Natural Pathways

  • Invasive species also invade ecosystems naturally.
  • Natural forces such as wind storms, ocean waves, and hurricanes can carry them over long distances. Also, they can hook onto other animals and ride to new locations. 
  • Seeds also spread in natural ways. Then they will land and grow in areas they don’t belong.

and take over native plants.


Invasive species hurt the ecosystem in several ways. Additionally, they harm the environment. Finally, they can threaten people and other plants or animals. 

  1. Reduced Biodiversity

  • Biodiversity is the variety of animal and plant species in a habitat. Biodiversity is very important to ecosystems.
  • Invasive species change habitats.  Then they hurt the native species. Also, invasive species compete with native species for limited natural resources. They can use up the land, food, or water.
  • Sometimes invasive species are predators.  A predator is an animal that preys on and eats other animals. So, the invasive predator can kill off native animals. This causes the loss of biodiversity over time.
  1. Extinction of Native Species

  • When an invasive species is introduced into an ecosystem, it can wipe out both plants and animals.
  • The extinction of native species is a great danger. Basically, once the habitats are so damaged the native animals die off. 
  • Invasive species can introduce new diseases. Then these new diseases kill the native species. This is because the native plants and animals can’t handle the new disease. 
  1. Degradation of Ecosystems

  • Invasive species change ecological processes in an ecosystem. An ecological process is a special way an ecosystem works.  They change how plants and animals work together.
  • The invasion of ecosystems also causes a loss of food for native species. This will leave the native species with nothing to eat.
  • Invasive species change the food web. Basically, they make it harder for native animals lower on the food chain to get food.
  1. Water Scarcity 

  • Invasive plant species change the availability of water in an ecosystem. Those that grow well in wet places use up water. Then there are water shortages.
  • Invasive plants stop streams from flowing. Then the water doesn’t make it to the habitats in the ecosystem.
  • Invasive ocean plants change ocean biomes. Then, food can’t move well for native species in the oceans. 
how invasive species affect humans


Invasive species harm people in many ways.  (Research from Britannica)

  • Effect of Invasive Species on Human Health

-Alien species are a threat to our health. Some invasive species bring new diseases. 

-Many invasive species carry existing diseases. For example, the Asian tiger mosquito carries Dengue fever. Dengue fever has invaded parts of Europe and is a big problem. 

  • Economic Impact of Invasive Species

-Invasive species harm the economy. Alien plant and animal species cause problems for farmers. New pests cause damage to crops. Then people have food shortages.

-Some invasive weeds hurt soil nutrients. Then, farm plants can’t grow well. 

-Invasive ocean species hurt fishermen. Basically, the invasive species hurt the native fish people eat.


Just about any species can become invasive. Basically, if a species moves to where it doesn’t belong it is invasive. 

Examples of some of the most invasive species:

  • Cane Toads. The cane toad is a highly poisonous toad. It is native to Central and South America; however, they were deliberately brought to Australia from South America in the 1930s as a method of controlling pests on sugarcane plantations.
  • Zebra Mussels. The zebra mussel is a fast-spreading species in freshwater lakes. They move into new habitats by attaching to boats and ships. They were accidentally introduced to North America in the 1980s, likely through ballast water from ships coming from Europe.
  • Asian Carp. Asian carp are an invasive species in several waterways in North America, particularly in the Mississippi River Basin and its tributaries. They were originally introduced to the United States in the 1970s to control algae growth in aquaculture ponds and wastewater treatment systems.
how invasive species spread


Invasive species are a serious threat in the United States. Almost all states in the US have invasive species. (Research from USGS Research for a Changing World)

  • The US has over 6,500 non-native species. More than 4,000 of them are invasive. This includes both plants and animals.
  • Globalization is one reason for invasive species in the US. Many animal species came into the US with ships. 
  • Scientists also brought new plant and animal species in for research purposes.
  • Some invasive species in the US are the Burmese python, Kudzu, Feral swine, and the Common starling.


Invasive species cause great habitat damage in an ecosystem. Vulnerable species or endangered species often go extinct because of invasive species. Overall, invasive species are a major threat to biodiversity and ecosystem health. It is important to prevent their introduction and manage their impacts in order to protect native species and maintain healthy ecosystems.

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