Swamp pink: measuring the few inches around a plant

Protection preceded a detailed hydrologic test

The Fish and Wildlife Service published its final determination listing swamp pink as threatened on September 9, 1988. The earlier proposal identified filling, drainage and private collecting among the threats and placed many known populations in New Jersey. These are dated conservation records, not a present-day count of every surviving colony. USFWS final listing, September 9, 1988; USFWS proposed listing, February 25, 1988.

Plants occupied particular parts of the hummocks

Kim Laidig, Robert Zampella and Carlo Popolizio studied two streamside colonies and published their results in 2009. They measured water levels over two years and related them to 958 clusters, usually growing on exposed portions of hummocks. The plants were not spread uniformly across all available wet ground. Laidig, Zampella and Popolizio, Journal of the Torrey Botanical Society (2009).

When the researchers simulated a fifteen-centimeter drawdown, more than thirty percent of existing cluster area at both sites fell into unusually dry conditions by their study’s definition. A thirty-centimeter reduction affected all or nearly all cluster area. These were modeled exposures, not observed deaths caused by experimental pumping. Laidig, Zampella and Popolizio, Journal of the Torrey Botanical Society (2009).

Newly exposed ground was not an automatic replacement

Lower water could also expose ground that had previously been submerged. The authors stressed that its value as replacement habitat depended on whether swamp pink could colonize it. That unresolved step matters: a map of apparently suitable substrate does not prove that a slow-moving plant population will occupy it in time. Laidig, Zampella and Popolizio, Journal of the Torrey Botanical Society (2009).

Decline without an obvious hydrologic change

The Fish and Wildlife Service’s September 2021 review described two Camden County colonies declining between 1998 and 2017 despite monitoring that found no corresponding deterioration in hydrology or vegetation. Deer browsing was suspected, but the original monitoring was not designed to isolate its effects. This added an important complication to the water-level story: maintaining wet conditions did not remove every source of population loss. USFWS swamp-pink five-year review (September 2021).

After a deer-exclusion fence was installed at one colony in November 2020, sampled flower racemes increased from one in the 2020 baseline survey to sixteen in April 2021. The review treated this as an encouraging initial response requiring further monitoring. It was not yet proof of lasting population recovery, and the comparison did not erase the separate evidence that groundwater changes could threaten other colonies. USFWS swamp-pink five-year review (September 2021).