Thread by @Plants__Animals

What are invasive species?

Global trade is bringing invasive species to new environments around the world. Is that always a bad thing?🤔

Continue reading this thread to learn more about these species.

1) An invasive species is a type of animal, plant, fungus or any other living thing that has arrived in a new environment and can harm other species there. You might hear the term "invasive species" used interchangeably with...

2) "naturalized species," "exotic species," "noxious species" and "non-native species." Although each of these terms has a slightly different meaning, they all refer to members of a species living in an area they aren't originally from.

3) Species invasions are on the rise: Of all invasive species discovered during the past 200 years, about 40% were discovered after 1970. Often, invasive species arrive in the new environment as people's pets, additions to someone's garden or stowaways on a boat.

4) Global trade regularly carries species to new places around the world, inadvertently or deliberately. It is suggested that the recent upswing in invasions has been propelled by globalization, economic growth and more efficient international transportation.

5) The countries with the highest number of invasive species include the United States, France, Australia and China, a 2016 study in the journal Global Ecology and Biogeography found.

6) Example: In 2010, scientists discovered Austropuccinia psidii, an invasive fungus from South America, in Australia. When the fungus spreads on Australia's eucalyptus trees, it takes over, stripping their branches of leaves, stunting their growth and sometimes killing them.

7) This fungus is an example of how invasive species can directly harm native species — in this case, by killing them. But other invasive species harm native species indirectly. For example, fish called bighead carp (Hypophthalmichthys nobilis) were brought to the US from...

8) China in 1973 and now swim around the Mississippi River watershed, gorging on plankton. Plankton form the base of the watershed's food web, so when the carp eat the plankton, it results in a food shortage for small, native filter-feeding fish.

9) When these small fish starve and subsequently disappear, so do the bigger fish that eat them. In this way, the carp create a nutrient shortage that ripples through the ecosystem.

10) Other invasive species prey on native species or compete with them for water and habitat and, in doing so, threaten #biodiversity

11) Invasive species can also cost people a lot of money. For example, new pests or pathogens can threaten crops and aquaculture. Invasive species management and damages have cost an average of $26,8 billion USD globally since 1970.

12) By definition, invasive species can harm other species in their new environment, but that doesn't necessarily mean they will.

13) Of those that establish themselves in the new environment, some invasive populations will grow abundant, while others will remain small and innocuous. In rare cases, invasive species may even benefit some members of their new environment.

14) Take the tamarisk, for example. This genus of Eurasian shrubs was introduced to the United States as an ornamental plant in the 19th century and has since spread throughout the western U.S.

15) The tamarisk causes problems: It sucks up a lot of water and secretes salt into the ground, thereby preventing native trees from growing around it.

16) However, an endangered bird called the southwestern willow flycatcher has begun breeding and feeding on the tamarisk, at least since the 1990s. In this case, the invasive shrub is hurting some native species while helping another, by providing habitat to a bird in need.