Ethics of Planting Natives - Understanding EcoRegions and Nativity

Asked March 10, 2020, 9:38 AM EDT

We often hear of the ethical issues associated with planting Invasives, Cultivars with unknown value to pollinators and even Nativars (and cultivars) that inter-breed with our Native Plant species. There is also an issue with planting Maryland Natives outside their home EcoRegions. This can be especially complicated by those plants that are wind pollinated that can easily escape (the planted area) - highlighted when those species are on protected, threatened or endangered plant lists. This could cause botanists to miss-identify these in a non-native ecoregion as native confusing the Nativity status and potentially consume State funds in conservation efforts that are not warranted. What information exists on this topic? What is the recommended practice as more and more people week to establish Native landscapes?

Howard County Maryland

1 Response

This is a very complex issue; bear in mind that these various factors can work in concert and a lot of overlap is likely. Various discussions on this topic are linked here:

https://extension.umd.edu/hgic/topics/cultivars-native-plants

https://extension.umd.edu/hgic/topics/what-native-plant

https://news.maryland.gov/dnr/2019/10/18/the-cultivar-question/

Part of the problem stems from a lack of sufficient study to answer these questions. For instance, a lack of genetic profiling for populations known to exist around colonial times as a comparison to today's population genetics. Similarly, current habitat and growing conditions (temperature and weather patterns, pollutants) are likely different now than they were when the populations we wish to compare data with were present. Thus, what was historically suited to a site may no longer be the best choice. It is possible that certain genetic populations of a species are more well-adapted to current conditions than the historic populations, and thus they are the only option for practical, successful restoration. (For instance, a species with a range extending to our south may have better tolerances for summer heat and warmer winters that we are now experiencing; local populations would similarly drift northward for the same reason, as cold tolerance is no longer selected for as strongly.) Animal and plant species in some mountain habitats, for instance, have been observed shifting their ranges to higher altitudes to keep up with environmental conditions needed for them to survive. From this perspective, it may not make much sense to try to re-establish "original" populations when their conditions favoring growth may not still exist. If the site conditions can be restored to pre-colonial conditions, the consideration over "pure" population genetics may be more applicable.

Native plant population ranges are known to shift over time (usually geologic time). Consider, for instance, populations that did not reclaim their original range after glaciation pushed them south. Their associated fauna (either insect pollinators or animal seed dispersers) may or may not change their range in concert, affecting how the plant genes will move through existing populations. Think of the megafauna no longer present to disperse the seeds of Osage-Orange throughout its former range.

For simplicity's and practicality's sake, homeowners are encouraged to seek natives that are known to be native to the broadly applicable habitat (physiographic province: mountain, piedmont, coastal plain) of their location. Publications such as this one are written with this in mind: https://www.fws.gov/chesapeakebay/pdf/NativePlantsforWildlifeHabitatandConservationLandscaping.pdf. If a native species (regardless of ecotype) is used in a location in place of a non-native, there is at least a good chance it has greater ecosystem value and, if sited properly, may also stand a better chance of surviving unaided resulting in minimal inputs of water, fertilizer, or pesticide. (Granted, some invasive species thrive just as well as some natives, but typically they need to first get a foothold by establishing in disturbed and degraded sites.) As such, promoting native plant use in gardens is likely to be beneficial as a whole; locally-sourced genetics is sensible and probably the most practical for adaptability, though sources for such propagules is spotty at best.

Miri