What are they and why do they matter?

Invasive Species take over everything!  Technically speaking, they are plants and animals that did not co-evolve within the ecosystem they are occupying.  They tend to be more competitive, aggressive and greedy in their quest for moisture and nutrients.  They crowd out slower growing natives, usurp niches, have the ability to type convert an ecosystem into a mono-culture, and generally do not participate in the co-existent, sometimes symbiotic relationships between native plants and animals. 

Spotted-knapweed infestation

Tamarisk in riparian habitat

Perennial pepperweed

Habitat Works has

• Patrolled 256 miles of stream, mechanically and chemically treating tamarisk wherever it's found
  
• Removed 97,793 tamarisk plants from riparian habitats
  
• Removed 68,671 other invasives species from recovering post-fire and similarly sensitive habitats
  

Riparian Invasives

     Due to the sheer volume of plants and animals that depend on water, riparian ecosystems (along streams, rivers and other waterways) contain the most biodiversity of any other location within an ecosystem.  When invasive plants move in, they crowd out natives and the animals that depend on them.  Left to extremes, entire ecosystems can be type-converted into mono-cultures of invasives.  A classic example is the tamarisk-only habitats we see along the Colorado River in Southern California's deserts.  

Control Methods

     In the many places where herbicides are not practical nor approved, Habitat Works endeavors to keep invasive plants in check through mechanical means.  We have found that by visiting sites inundated with invasives and repeatedly cutting them to grade, they do eventually die.  We have had great success with this method on Upper Piru Creek, covering the 38 mile watershed several times over, and bringing the tamarisk infestation largely under control.  
    There are some locations where herbicide is approved for use under stringent regulations, and we bring it to bear on the the problem of persistent invasives.  This is a highly effective method for dealing with invasives in remote, rugged areas, where left unchecked, mature invasives become a powerful seed source for all areas down stream.

Post-Fire Invasives

     After fire, conditions are great for invasive plants; wide open space, sunshine, freshly released nutrients, disturbed soil structure and little competition.  Southern California's native chaparral is adapted to the uncertainty of annual rainfall and is conservative in the use of water and nutrients.  It's easy for invasives to get a hold in new territory, quickly making a grab before charred natives begin recovery.  It is important to monitor post-fire recovery areas for infestations, and to control their spread while the native habitat reestablishes.

Current Projects

     Habitat works is currently treating invasive species in several areas of ecological concern.  Sign up on our e-list for project updates.  We'd love to have you join us!

---