“On the topic of so-called ‘invasive’ plants, we don’t have an axe to grind, but there sure is one we would like to dull.”
“The Troubles of ‘Invasive’ Plants” is a 21,000+ word project by Nicole Patrice Hill & Kollibri terre Sonnenblume for Macska Moksha Press. Excerpts are posted online (see below), but the full version is available only as a zine that you can download here free-of-charge.
Hardcopies are for sale here.
This is part three of a three part series. Read part one & part two. The full series, along with additional material, is available as a zine, here.
Dandelion (Taraxacum officinalis) [Photo by KtS]
By Nicole Patrice Hill & Kollibri terre Sonnenblume
Changing plant communities at the local scale are symptomatic of the changing climate globally. Patterns of temperature, precipitation and seasonal timing are shifting, and with them, the patterns of birth, growth, reproduction—and survival—of all living creatures.
One widely observed syndrome is “season creep,” in which Spring has been arriving progressively earlier in the calendar year. This does not mean that every Spring starts sooner than the year before, but that an overall trend has been observed. For example, a survey of leafing, flowering and fruiting records from 1971-2000 for 542 plant species in 21 European Union countries showed advanced timing for 78% of the plants. According to other sources, “Spring events, such as blooming, frog breeding and migrant bird arrivals, have advanced 2.3 days per decade.” Winter snow cover duration—as measured from Fall to Spring—has decreased throughout the Northern Hemisphere since 1978. The earlier the snow melts, the less water is available during the hot summer, which affects a wide range of plants, animals and other life.
Winters have been warming. For example, the average February maximum temperature in the US rose by 0.3 F per decade from 1895-2016. This general rise in the “floor” has been accompanied by an increase in “extreme” events, such as “false Springs” when temperatures warm up enough to trigger life cycle stages in a variety of species. When more “normal” weather arrives later—or another extreme event follows, but this time on the cold side—a plant can be injured or even killed. A common example is when a hot spell causes fruit trees to flower, and then a frost—even just a “normal” one—zaps the flowers, thereby taking out that year’s harvest.
When we were farmers, we experienced how extreme events affect crops. In the Spring of 2013, periods of warmer-than-average weather alternated with periods of colder-than-average weather a few times, and the transitions between them were quick, as in 36 hours. Spring greens thriving in “normal” cool temperatures would go to flower prematurely when the temperature rapidly heated up. Then, warm weather crops would stall out when the temps fell. Annual vegetable plants don’t do well with such erratic conditions and we watched helplessly as our failure rate climbed.
This is part two of a three part series. Part one can be found here.
Saltcedar trees at an undisclosed location in southern California [photo by KtS]
Popular ideas are not always factual ideas.
When the subject is a particular “invasive” plant species, common assumptions about its undesirable impacts are not always scientifically documented or even true. Add to this an inherent bias in the field of invasion biology for interpreting nearly all effects of non-native plants as detrimental without considering the possibility of positive outcomes and you’re sure to get villains nearly every time.
Let’s look at two well-known examples of so-called “invasive” plants that are under the gun: Tamarisk, aka Saltcedar (Tamarix spp.) and Russian Olive, aka Oleaster (Elaeagnus angustifolia). In the western United States, these two trees are now the third and fourth most frequently occurring woody riparian plants, and the second and fifth most abundant species along rivers. To eradicate them would entail destroying a significant amount of healthy vegetation (with no little amount of collateral damage to other flora) and would incur a hefty cost. Congress authorized $80 million for Saltcedar removal between 2005 and 2009, which included herbicide,[1] but that is pennies compared to what would be needed for everything. So the case for removal needs to be strong.
But the case is not strong. The main claims made against both species are that they a) push out native flora, b) monopolize groundwater, and c) don’t provide for native fauna. Saltcedar is additionally accused of increasing the salinity of its immediate environment. Yet these claims have never been proven and plenty of evidence to the contrary has been produced.
St. Johnswort (Hypericum perforatum) [photo by KtS]
This is part one of a three part series. In this part we discuss: a) the negative effects of invasive plant removal methods, b) the involvement of Monsanto in popularizing invasion biology, and c) the tragedy of Pinyon-Juniper forest eradication in the western U.S. under the rubric of “native invasive species management.”
Defining “invasive species” is a slippery proposition.
The U.S. federal government defines it as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”
The National Wildlife Federation elevate s environmental considerations, describing it as “any kind of living organism… that is not native to an ecosystem and causes harm.”
The Connecticut Audubon society is less discriminating about the effects of introduction. For them, an invasive is any “non-native species that has been introduced, either intentionally or accidentally into a new habitat or has escaped cultivation.”
A plant species doesn’t have to venture far outside its native range to be considered invasive. Such is the case of the endangered Monterey Cypress (Cupressus macrocarpa), which “ is a frequent target for the chain saws of the San Francisco Recreation and Parks Department—even though two small stands in Monterey, just fifty miles south, are cherished and protected as natives.” Meanwhile, a 500 mile drive north of its relict range , a large specimen planted by European settlers in the 1850’s is an officially designated “Oregon Heritage Tree,” which we assume grants it some safety.
