Monday, January 01, 2007


Islands are interesting habitats from an invasive species perspective - little chunks of land to which there are few vectors of introduction. States, provinces, even countries might act like they are islands, but their borders are virtually ignored by nonnative plants and animals.

This is one of the reasons why the Electronic Field Guide to the Invasive Plants of Nantucket is so interesting. On first glance, it reads like a who's who of invasive plant fact sheets. But it is worth a closer look, and not just because I am one of the authors of the project :-).

The 78 plant species currently listed were subject to a risk assessment modeled after the one completed by the state of Massachusetts (.pdf), but focused on Nantucket. One of the most interesting things, to me, is to compare the resulting list to the one compiled for the whole state. For example, there are species listed as invasive by the state of Massachusetts that have never been found on Nantucket Island, like glossy buckthorn (Frangula alnus) and lesser celandine (Ranunculus ficaria). Why are they not on Nantucket? Are conditions inhospitable or are there no vectors of introduction? Certainly special attention needs to be paid to prevent these known invaders from becoming established on the island.

There are also species categorized as invasive on Nantucket that are not considered a problem by the state of Massachusetts, like saltspray rose (Rosa rugosa) and white poplar (Populus alba). Also, we include pitch pine (Pinus rigida - likely a controversial listing since pitch pine is native to Massachusetts but not to Nantucket. Terms like "widespread" and "dense stands" can take on a different meaning when the area being evaluated is an island covering less than 50 square miles.

You can explore the guide on your own using the Search link on the website (left side of the page). Of course, the usual disclaimer must appear here: The plant list compiled for the Electronic Field Guide to the Invasive Plants of Nantucket has no legal status.


GreenmanTim said...

As one who was heavily involved in the Massachusetts Invasive Plant Advisory Group's assessment of species meeting criteria for invasiveness in the Commonwealth or likely to become so, I find comparisons to Nantucket's process of evaluation very interesting. Nantucket's unique geography, not only as an outlying island but (thanks to the Gulf Stream) as the most temperate climate in the State, make it a special case.

As you know, the criteria developed by MIPAG for assessing species invasiveness were applied statewide. Some plants with restricted ranges (e.g. Glaucium flavum)nonetheless met the full criteria, while others (Populus alba and Rosa rugosa) required more data to establish whether they were truly outcompeting native plants. In both of these cases, while there were reasons for concern the standard for conclusive "non-anecdotal" evidence of invasiveness in Massachusetts was not reached. New data will prompt new re-evaluation.

Nantucket is thought to be a likely point of introduction for species with the potential to become invasive in Massachusetts but not yet recorded in minimally managed habitats in the State. It is therefore one of the best places to refine early detection / rapid response strategies.

There are other considerations specific to Nantucket's ecology that would suggest different conservation goals and different species that would be management concerns. Given the behavior of Populus alba in Orleans, Nantucket is wise to be concerned about its potential impacts.

Pitch Pine surprises me. Is there indeed no evidence in the paleobotanical record for this early colonizer of the non-glaciated landscape on Nantucket? What is it displacing? Scrub oak heaths/huckleberry barrens?

Jennifer Forman Orth said...

We can never rest on our laurels with any of these risk assessments, since the plants in question are not likely to remain in stable distributions, and there will always be new species to evaluate. Now that teams on Nantucket are collecting data for IPANE, I hope that the island data can contribute more to future assessments done for the state as a whole.

Regarding pitch pine, we have yet to discover any paleobotanical studies, but I have a feeling if there are any, the publicizing of this project will help uncover them. As far as I know it was introduced intentionally in the 1800s and then practically wiped out again in the 1920s (due to lumber needs and grazing), followed by more introductions. Now it causes problems as a successional species, and specifically displaces native plants in sandplain grassland habitat (The Japanese black pine are quite numerous there as well).

Even if someone produced a pollen core...I'm not convinced that means pitch pine should be considered a part of Nantucket's natural landscape. Maybe a consult with Floyd the Utah Flamingo is warranted...;-)