Wetlands of Florissant Fossil Beds National Monument, 2009–2019

By Sonya Daw, Billy Schweiger and Dana Witwicki, Rocky Mountain Inventory and Monitoring Network, National Park Service

A foot trail right beside a monitoring site at the Barksdale wetland complex. The trail likely changes the site's water flow and brings more human disturbance. NPS/Schweiger.

Sedges, mosses and many other water-loving plants grow in the wetlands of Florissant Fossil Beds National Monument, Colorado. But disturbance, past and present, and a changing climate affect their condition. As the climate warms and drought grows, managers need information to make the wetlands more resilient and to guide restoration.

Since 2009, scientists of the Rocky Mountain Inventory and Monitoring Network have tracked the wetlands' climate, human disturbance, groundwater, soil and water chemistry and vegetation. This summarizes results through 2019 from fens and wet meadows at 10 sites in 3 wetland complexes: Hornbek, Red Barn and Barksdale.

The three wetland complexes monitored. Photos, top to bottom: Hornbek, Red Barn, Barksdale. NPS.

Condition at a glance

Wetland condition, 2009–2019. Green: good; yellow: intermediate; red: deteriorating. Arrows show the direction of change; a heavier circle means higher confidence. NPS.

Climate

Some of the most worrying stresses come from climate, projected to grow warmer with variable precipitation. Models predict hotter summers, less snow and earlier peak streamflow in the region, likely leaving less water for wetland plants.

• This climatic water deficit raises the risk of drought stress and is expected to shrink the number and area of the park's wetlands.
• Two droughts hit the region during the study: 2009–2013 and 2017–2019.
• The team's modeling suggests climate change may lower groundwater, with important effects on wetland plants.

Disturbance

Human disturbance — including a century of cattle ranching — affects the wetlands at several scales.

• Landscape scale (farming, development, roads and trails): lower in the valley bottoms, where many wetlands lie, but higher where sites were near roads.
• Local scale: water diversions, and physical or chemical effects such as bank stability, algal blooms, turbidity and heavy metals, which hit plants directly. Most sites were intermediate, and local disturbance fell from 2009 to 2019.

Grape Creek at the Hornbek complex, before (2009) and after (2013) restoration: the deeply cut channel has filled in and recovered. NPS/Billy Schweiger.

Groundwater

Wetland plants need a steady, shallow supply of groundwater.

• Wetness, measured once or twice each summer at every site, rose from 2009 to 2019 — perhaps mostly in the fens.
• But compared with wetlands across the ecoregion, the park's were drier than ideal, so overall hydrologic condition is intermediate.

The Hornbek puzzle. Automated loggers record groundwater continuously at some sites. At Hornbek, work to fill in cut channels finished in October 2012, and water tables rose afterward. But 2011–2013 was also a drought, and there are no data from before 2011 — so it is unclear whether the stable, high water tables from 2014 came from the restoration or the return of wetter weather. Either way, plants got more water in the growing season, and the restored site seemed more resilient to the 2017–2019 drought.

Heavy moss cover at the Hornbek fen. NPS/Billy Schweiger.

Vegetation

The plants a wetland supports reveal its condition. Four measures were used:

All four showed stable, healthy conditions — except native species cover, which was intermediate. Right after restoration, some Hornbek sites had nearly 50% invasive cover, though it decreased later.

How it fits together

Human disturbance, especially where it changed groundwater levels, hurt wetland health. At some sites, plants suffered from the density of nearby road–stream crossings and other land uses. Tracking this link is central to the network's monitoring, with direct uses for management.

For managers

Continued monitoring shows where nonnative plants occur, and how and where disturbance is affecting native plants and groundwater. Knowing each site's condition helps prioritize restoration. Recent research suggests the effects of climate change can be offset by reducing other stresses — for example, raising groundwater through restoration — and as a protected area, Florissant is well placed to do that.

New tools help:

• a Climate Projections dashboard for the monument, including fire ignition projections, on climateanalyzer.org;
• water balance modeling, which could also be built for Florissant's wetlands to guide restoration timing and priorities;
• vulnerability assessments of key natural resources.

Full report: Schweiger, E. W., J. Lemly, D. Witwicki, K. Sherrill, R. Whittington, L. Messner, E. Cubley and K. Haynes, Florissant Fossil Beds National Monument wetland ecological integrity: 2009–2019 synthesis report, Natural Resource Report NPS/ROMN/NRR—2023/2577. Also a printable brief.

Sources

Based on "Climate, Disturbance, and Wetland Condition at Florissant Fossil Beds National Monument, 2009–2019," by Sonya Daw, Billy Schweiger and Dana Witwicki, National Park Service; a work of the United States government in the public domain. Its water-balance diagram, adapted from a journal article, is not reproduced.