I've wondered about this notion of native species also being "invasives." Here in the southern Great Plains and adjacent Cross Timbers terrain Eastern Red Cedar (Juniperus virginiana) is native. Formerly it was rare outside of zones protected from fire by topography. It occurred on steep sites, in riparian zones, and in canyons where fire seldom reached. Today, there are broad swaths of former prairie that have become closed canopy cedar forest, and wherever one travels, one can see pastures and prairies that have young cedars growing thickly through them. The plant is not grazed, most wildlife does not eat it, the cedar thickets have been shown to have very low native bird diversity compared to adjacent woodlands and prairie. For the most part, these have developed in the past thirty years as heavy grazing and fire prevention/suppression have become the norm. Extension Service, The Nature Conservancy, and other agencies treat Eastern Red Cedar as a pest, and work to! eradicate it, as do many individual landowners. In fact, through misreading of promotional materials, some folks mistakenly believe the plant is not native in this area.
So, is this a native invasive? Or just a giant weed (and what is the difference?). mcneely ---- "Warren W. Aney" <a...@coho.net> wrote: > Wayne, part of the challenge in defining invasives is keeping it simple > while making it complete. For example, the word "native" may or may not > cover all invasives. Also, there can be non-human caused introductions or > spread. > The barred owl is native to North America. Its recent non-human induced > spread in range and its resultant harm to endemic spotted owl populations > would appear to quality it as an invasive, even though it doesn't fit some > of the cited definitions. > Reed canarygrass may be indigenous but its monocultural takeover of wetlands > means it is classified as an invasive on most lists. Some of its spread has > been due to cultivation use. > So to me, the definition of an invasive is a species whose presence and > spread reduces natural ecosystem qualities such as diversity, productivity, > stability and resilience. > > Warren W. Aney > Senior Wildlife Ecologist > Tigard, OR > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news > [mailto:ECOLOG-L@LISTSERV.UMD.EDU] On Behalf Of Wayne Tyson > Sent: Sunday, 01 May, 2011 18:29 > To: ECOLOG-L@LISTSERV.UMD.EDU > Subject: [ECOLOG-L] Science Ecology Terms Definitions Invasive etc. > > Ecolog: > > Some may find it informative or ill-informative to follow the bouncing links > on this site (they come up as pdf files). > > I am particularly interested in all ecologists' views of the definition of > "invasive species," (here reproduced for your convenience), but there also > are other flaws. Does ESA agree (aside from grammar nit-picking) with the > text of the cited "laws?" > > http://www.iscc.ca.gov/cisac-strategic-framework.html > > INVASIVE SPECIES > > > What is an Invasive Species? > > The ISCC Bylaws define invasive species as "non-native organisms which > cause economic or environmental harm." The bylaws clarify that invasive > species within the scope of the council do not include humans, domestic > livestock or non-harmful exotic organisms. > > This matches the definition established at the federal level by > Executive Order 13112 in 1999, which established the National Invasive > Species Council. It defines invasive species as "alien species whose > introduction does or is likely to cause economic or environmental harm or > harm to human health." The order clarifies that alien species are those > introduced to an area, whether intentionally or unintentionally, as a result > of human activity. > > California Food and Agricultural Code (Section 5260.5) defines > "invasive pests" as "animals, plants, insects, and plant and animal > diseases, or groups of those animals, plants, insects, and plant and animal > diseases, including seeds, eggs, spores, or other matter capable of > propagation for which introduction into California would or likely would > cause economic or environmental harm." > > Invasive species come in all shapes and sizes, and their impacts range > from clogging water pipes to killing wildlife, from ruining crops to posing > a human health hazard. Many organizations are involved in addressing > invasive species in California. The ISCC and CISAC formed to coordinate and > strengthen the efforts of these organizations. > > > > > WT -- David McNeely
