Native Range Maps FAQ’s

We recently finished uploading BONAP native range maps to our website. There is one at each species’ product detail page (except for a few species—maps forthcoming). The maps have generated a lot of good questions so we have created this blog entry to answer them. Please continue to ask questions below in the “Speak Your Mind” section of this blog to continue this Q & A session for all to read.

Question: Can you explain the coloring system more?

Answer: The following key to the map colors provides more detailed explanations than the key that accompanies the maps on our website. Notice that although there is county-level data for species occurrence, native status is only indicated at the state-level:

	Present in state: This color fills the background of any state or province in which the North American native plant occurs–or occurred historically–whether or not it is native to that particular state. It does not mean the plant occurs in every county in that state.
	Not present in state: This species is not believed to occur in this state or province outside of cultivation.
	Present in county, native to state: This color does not necessarily mean that the species is native to the county. It is native somewhere in the state, but its presence in the county could be the result of introduction from elsewhere in the state.
	Present in county, not native to state: This species has been introduced to this county. Furthermore, all occurrences in this state are due to introduction.
	Present historically, now extirpated: This species once grew in this county, but has become locally extinct.

 

Q: Can I plant a species outside of its range on the map? Should I?

A: In many cases the answer to the first question is yes. Our range maps are not hardiness maps—they do not show where a species can or cannot be planted and survive. Rather, they show where self-reproducing, wild populations are documented to occur. North American native plants can often be planted outside of their native range. When a species has become naturalized in a state outside its native range, it is represented by the blue counties in our range maps.

While some people believe that introducing North American native species beyond their native range is harmless, some restorationists, conservation biologists and others object to it. Wherever you stand on this issue, it is always important to avoid introducing new species to sites near remnant native plant communities (for example, state natural areas). In fact, when planting in the vicinity of remnants one should not only use strictly native species, but should furthermore use seed or plants of local genetic origin.

Q: Are these maps the same as on the USDA website?

A: The USDA range maps indicate whether a species is native or introduced to the continent of North America. The BONAP maps indicate whether a species is native or introduced to a particular state or province. As an example, compare the USDA maps to the BONAP maps for Amorpha fruticosa or Agastache foeniculum. The USDA maps give the impression that these species have wider native ranges than the BONAP maps indicate.

Actually, much of the data that USDA uses for their maps came from BONAP. BONAP no longer supplies data to the USDA, but continues to update its independent database, and has added hundreds of thousands of county records since then. Furthermore, BONAP has deleted many county records that, upon investigation, turned out to be in error.

Comment: A word of caution. Not all the information that went into these maps has been properly vetted. I know for a fact that there are mapping errors in the state where I work. Don’t trust all of those outliers.

Response: This comment reminds us that these maps are drafts. There are county occurrence records that are in error, and there are counties where species occur but have not been recorded. There are even local experts who would dispute the native status of some species in some states. With time BONAP will refine their database, but there may never be a perfectly accurate and complete picture. The range maps we have right now provide general outlines with some rough edges. The edges may be more rough in some states than others.