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.
