Sourcing Seed is Risky Business (or it should be)
In the spring of 2006 I organized an all-day symposium at the American Museum of Natural History entitled “What is Local?”, bringing in experts from across the country to present and explore what was already a long standing and seemingly intractable question—how far away can I safely go to source seed for my work? Today that question still remains open ended and largely unresolved.
The gold standard approach would identify Seed Transfer Zones (STZs) for each species. Through well-established techniques called Common Garden Studies and Reciprocal Garden Studies, investigators can determine with a reasonable degree of certainty whether or not seed from a given source will integrate into a chosen outplanting site. One measure of this is mortality; another is mean population fitness, measured at the planting site to quantify whether the newly established population is more, or less, fit or unchanged. Ideally, these measures would be collected over an extended period to ensure they reflect adaptation over time (more on this in a future blog). While not complicated, these studies are beyond the means of most native plant consumers. Few STZs have been established for the thousands of plant taxa native across the U.S.
Over the decades, Provisional Seed Transfer Zone short cuts have evolved using mapping and modelling to approximate STZs. Many of these now incorporate models to predict movement of populations in response to shifting climates.
Notwithstanding these tools, the selection of seed source for production and outplanting mostly proceeds with varying degrees of uncertainty as to the suitability of the source seed.
At the Greenbelt Native Plant Center—which I ran for twenty five years—we too had to deal with this uncertainty. Roughly 750 species, about one third of the original flora, remain in the various parks and other natural areas of NYC. Unfortunately, many of these populations are very small, as well as vulnerable to invasives, fragmentation and habitat loss and trampling; in Staten Island, these problems combined with the back migration of deer and resulting intense herbivory. All of these factors render the local landscape no longer suitable for seed sourcing. GNPC seed collectors have had to rely heavily on collections from outside of the City, particularly Long Island, New Jersey and to some extent the lower Hudson Valley. It’s practice has always been to carefully match source location to outplanting locations, and to record detailed information about seed source. Source information was preserved through all our production protocols, too, so that every plant leaving the nursery could be identified to source.
Implicit in our protocol was an element of risk assessment as to our sourcing and production decisions. Risk management is a discipline applied to all kinds of real world decision making. When it comes to planning habitat management and restoration work, risk management techniques are generally applied by developing a suite of alternative project scenarios and choices and selecting which will serve to minimize risk of failure to the greatest degree while remaining within the project budget.
Unfortunately, the same approach is rarely taken when it comes to seed source selection. Most often projects will make some specification as to source, such as political boundaries, but generally not with the degree of ecological specificity that would ensure integration into the outplanting site, including genetic integration. Worsening this situation is the fact that when it comes to procuring materials on the open market, more often than not there are no choices to be made and projects are forced to use whatever is available, sourced from wherever. MARSB’s 2017 survey of end-users in the Eastern U.S. showed that nearly 75% of projects could not procure plant materials from their preferred source and some were choosing sources as far away as 800 miles. Slowly, the situation is improving, but with the need for hundreds of species to be commercially developed from appropriate seed sources, we are still far from applying a meaningful risk management protocol to our source supply selection.
There are several take aways from this:
We need greatly expanded, systematic and sustained scientific collection and banking of wild seed in service to the supply chain that will then develop the necessary native plant materials to meet demand. MARSB’s first tier priority is to greatly expand seed collection and banking across the Mid-Atlantic states to meaningfully increase seed sourcing options and fuel production.
Seed collection and banking must be centralized to ensure both conservation of the wild populations that we are exploiting for native plant material development, and sound application of scientific protocols to sample, record and store seed sources for wild seed supply verity. Further, a well-funded and sustained cadre of botanically trained seed collectors is essential to ensuring these practices, and monitoring the health, loss and/or movement of populations over time—maintaining a real-time picture of source seed populations to inform seed sourcing decisions.
It is critically important as projects are staged and seed is sourced, however imperfectly, that sourcing information is recorded and maintained within the institution alongside records of outplanting decisions, so the opportunity to evaluate the success and failure of those materials is always available. In this way, every planting location maintains the possibility of yielding meaningful data about the suitability and sustainability of sourced material to that specific site. To the extent that projects have the resources, small experimental plots should be established within the larger project site—essentially becoming mini Common Garden Studies, available to future researchers to analyze for success and failure.
We must begin to routinely employ risk assessment in seed sourcing, which can only happen if we also have appropriate alternative choices from which to make that assessment—and in doing so, contribute to the overall health and sustainability of outplanting projects.
