What We’re Learning and Why it Matters: Long-Term Monitoring on the Northern Colorado Plateau

After more than ten years of monitoring, we've learned a lot about park ecosystems, how they're changing, and what they may look like in the future.

The National Park Service preserves America's most special and treasured places. Knowing which key natural resources are found in the parks, and whether they are stable or changing, can help park managers make sound, science-based decisions about the future.

The Northern Colorado Plateau Network (NCPN) is one of 32 inventory and monitoring networks building that knowledge. In 16 National Park Service units, our scientists and partners collect long-term data on key natural resources—like plant communities, soils, and the quality and quantity of water that we call "vital signs." Their condition can indicate the overall health of park resources. We analyze the results, track the changes, and provide information to decisionmakers.

There's still plenty we don't know, but there's a lot we do know. Here are some common questions and answers.

What have we learned? What kinds of changes are we seeing?

The first several years of any monitoring program are devoted to figuring out what's "normal" for a given system. We collect data to establish a baseline, then determine the range in which measurements might be expected to fall under typical conditions. With more than ten years of data for some resources, we've learned numerous key things about the systems we study.

Water Quality

The water quality in most NCPN parks is good. The most common issue of management concern seen in network data is waste contamination. Livestock, wildlife, and visitors can all be sources of waste contamination, including E.coli and emerging contaminants. Visitors can help keep park waters clean by using restrooms when available and eliminating waste more than 200 feet from water in the backcountry. Always filter water before drinking.

• Recent NCPN monitoring at eight parks during 2019-2022 found that water quality in network parks was generally good, though several sites exceeded state standards for water temperature, pH, and dissolved oxygen—conditions that can stress aquatic life. Continuous monitoring helps parks detect changes early, informing management strategies to preserve aquatic ecosystems.
• NCPN data have helped clarify the role of livestock in waste contamination at Zion and Capitol Reef national parks. The parks are working with the State of Utah to develop plans to reduce livestock waste in the affected streams and rivers. When we have good data on problems, park managers can work on making positive changes.
• Water temperature is another common issue. Fish, insects, and other aquatic species all have a preferred temperature range. As temperatures get too far above or below that range, aquatic organisms are unable to survive. In 2016–2018, at least one site in half the parks monitored had elevated temperature levels during the monitoring period. Water temperatures are expected to increase as climate change increases air temperatures and decreases surface-water flows in the U.S. Southwest.
• At Timpanogos Cave National Monument, long-term monitoring has revealed the influence of human activities on cave waters. At Hidden Lake, a decrease in dissolved CO₂ corresponded to implementation of a new cave management plan, leading to conditions that favored the formation of speleothems (cave decorations)-an important management goal in an active cave system. At Hansen Lake, trends in water chemistry mimicked trends that can be caused by air pollution. The only trend common to both pools was an increase in water temperature.

Big Rivers

• Variability is key to river health and diversity. They need dry years with low flows, wet years with high flows, and everything in between. Stability is generally bad for rivers, because a steady flow allows more vegetation to become established than a natural ebb-and-flow would. Once this happens, it is a lot harder for the river to do its job of reworking the riverbank. But when vegetation is occasionally scoured away, a diversity of physical and biological habitats is created.

• At Canyonlands National Park, the NCPN observed significant changes linked to dam-induced flow modifications. Reduced peak flows contributed to notable increases in vegetation and channel narrowing, especially along the Colorado River above Cataract Canyon, where vegetated area expanded by 28.8%. Occasional large flood events, like in 2011, temporarily reversed vegetation encroachment, highlighting the importance of periodic high-flow events in maintaining river ecosystem dynamics.
• Natural flows, and variable flows that follow natural flow patterns (e.g., on regulated rivers), result in lower levels of invasive plants. Stable flows from dams generally favor invasive plants over native plants.

Invasive Exotic Plants

Exotic-plant control works! Several parks have eliminated invasive exotic species from known locations, or made areas largely weed-free. NCPN monitoring results have reflected successful control efforts in several parks, including Colorado and Fossil Butte national monuments, and Zion and Capitol Reef national parks. These control efforts are most effective when the infestations are small. However, this work is never “done;” it’s an ongoing challenge. The NCPN monitors and regularly reports on invasive exotic plants at eight parks.

Landbirds

• Over 19 years of data collection, 16,996 point-count surveys have been conducted in the 11 monitored parks, detecting 166 unique species. In 2024, a total of 118 population-density trends were estimated across three habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Eighteen of those trends were significant (p-value < 0.05), including 7 declining trends and 11 increasing trends.
• Information from NCPN landbird monitoring can also be combined with other data, such as climate variables, to do vulnerability assessments, for instance, to evaluate how drought is impacting landbirds on the plateau.

Wadeable Streams

• Wadeable streams in NCPN parks are prone to flash floods.
• At Capitol Reef National Park, the potential for lower inputs and greater evapotranspiration suggest the Fremont River is at risk for progressively lower flows over time. Peak flows showed the greatest decreases.
• At Zion National Park, changes in these systems tend to be sudden and unpredictable, and longer-term trends can be hard to detect.
• At Natural Bridges National Monument, vegetation along wadeable streams tends to be well-adapted to disturbances.
• At Arches National Park, increased drought stress has already been noted during dry years. If its current protections are maintained, the primary stressors on the Courthouse Wash system are likely to be climate change and exotic-plant invasions.

Vegetation and Soils

• Across 10 years of monitoring at Dinosaur National Monument, multiple indicators suggested that plant community change is taking place in sagebrush ecosystems. A rapid, increasing trend in exotic cover and frequency, and a decreasing trend in the density of pinyon-juniper saplings, may be cause for concern.
• At Capitol Reef National Park, the NCPN is helping park managers learn how park grasslands have changed since grazing ended. In 2020, the network published a trend analysis of data collected at active and retired grazing allotments in the park’s northern section. In allotments retired since the 1990s, vegetation and soils were in relatively good condition, and trends were stable or improving. In the grazed allotment, condition was declining for 9 of 22 monitored parameters. Continued monitoring will help managers to know where restoration projects are most needed—and most likely to succeed. This helps ensure tax dollars are wisely spent.
• Seasonal precipitation was found to be an important influence on vegetation cover at Capitol Reef National Park. Looking at vegetation data in the context of climate data shows us how plant communities have responded to past patterns of temperature and precipitation. This helps us predict how current communities may respond to expected patterns of increased temperatures and decreased water availability. The record we’re putting together now can help park managers know what to expect in the future.

What are the current and expected effects of weather in network parks?

Long-term monitoring does more than tell us what’s happened in the past. It shows us how a system works under a range of different conditions. Once we have a long-term data record that reveals baseline data and past and current trends, we can determine how sensitive different vital signs are to weather conditions – and where, when, and how much they are likely to respond as weather patterns change.

What follows is a list of changes we are already seeing reflected in our data and the expected effects based on our own record and the best available climate models.

Water Quality

• Extended drought and hotter temperatures observed during the 2019–2022 monitoring period at eight NCPN parks contributed to streams drying out earlier and more frequently, reducing water availability and negatively impacting water quality. Increased evaporation and reduced flows from prolonged dry periods stress aquatic ecosystems and threaten park wildlife.
• A lot of NCPN surface water is vulnerable to hot, dry conditions. Measured springflow at Arches National Park is closely related to air temperature, because higher air temperatures mean more water is used by plants and lost to evaporation. That leaves less surface water for animals. The same process affects many smaller streams that rely on groundwater for much of the year. Extreme drought in 2018 caused one of our long-term water-quality monitoring sites to go dry and caused very low flows in others.
• We’ve recorded increasing water temperatures (related to increasing air temperatures) in places as diverse as cave pools, large reservoirs, and mountain streams. This can stress aquatic life—both directly and indirectly—through effects on things like dissolved oxygen. It also increases the likelihood of harmful algal blooms, like the ones that recently occurred at Curecanti National Recreation Area (2018) and Zion National Park (2020). Harmful algal blooms kill fish. They can also kill pets and cause severe illness in people. They are a significant public health risk and are likely to increase with rising temperatures.

• Wildfire often causes catastrophic changes in water quality and flood magnitude. A 2006 wildfire in Zion National Park’s North Creek drainage caused debris flows that were toxic to fish, overtopped culverts, and damaged homes downstream of the park. Algal blooms continued for years after the fire, which made the stream uninhabitable for fish. Wildfire frequency and intensity are expected to increase.
• Even if annual rainfall stayed about the same, a hotter future is effectively a drier future for NCPN parks because of increased water demand and losses to evaporation.

Big Rivers

• Reduced peak river flows due to dam management have contributed to increased vegetation growth and channel narrowing along the Colorado and Green Rivers in Canyonlands National Park. With ongoing drought and lower peak flows, riparian vegetation is expected to further encroach on channels, potentially altering river ecosystem dynamics and increasing susceptibility to invasive species like tamarisk.
• Recent years have been dry. The first-ever "call" on the Yampa River occurred in August 2018. Average flows on the Yampa River in September 2018 were 56.9 cubic feet per second (cfs), the second-lowest flow ever (the previous being 46 cfs in 2002). At Curecanti National Recreation Area, Blue Mesa Reservoir dropped to an elevation of 7,437.18 feet in fall 2018. This was the lowest it had been since 1984, when it reached its record low of 7,427.71 feet.

Invasive Exotic Plants

Once established, invasive exotic plant populations generally increase when left alone. They capitalize on habitat disturbances (such as wildfires, flooding, extreme droughts, construction activities, and other land-use practices), and then become established. Future climate patterns are expected to result in increasing numbers of environmental disturbances. This will increase opportunities for invasives.

Landbirds

Some NCPN landbird species will be more vulnerable to future warming and drying than others. When network staff and partners examined 12 years of landbird-monitoring data with long-term climate records, they found that some species decreased in density as drought stress increased. But other species showed a positive response to an increase in water deficit. The direction and magnitude of a given species's response was dependent on habitat type and species traits. Birds that breed in multiple habitats may find it easier to adapt to future conditions. These results will help land managers to focus conservation efforts on places where certain species are most vulnerable to projected climate changes.

Vegetation and Soils

• In 2017-2018, there were 16 consecutive months of below-average precipitation at the Natural Bridges National Monument climate station. This drought-the worst seen in 30 years-was more stressful for junipers in southeast Utah (e.g., Hovenweep and Natural Bridges national monuments) than previous local droughts have been. We and others are trying to figure out why. We will be investigating how many trees perished in the drought, and if vegetation recovers as it did from past drought (e.g., 1999- 2003).
• At Hanging Gardens, small populations of endemic plants have showed statistically significant declines when data were pooled across parks. Starting in 2020, we also noted potential die-offs of some endemic species at some sites, likely due to increasing drought. Drought effects were visible on other springs vegetation during site visits in 2020 and 2021, and we have noted mortality in spring-associated species at the edges of hanging gardens. As climate change continues, we anticipate additional drought stress and drying in hanging gardens and other springs in southeast Utah.
• The most recent drought has highlighted the way different plant types and species, like those at Dinosaur National Monument and Curecanti National Recreational Area, have different strategies to survive drought, and taught us a lot about what to expect as climate change progresses. For example, junipers kill off their own branches and may ultimately survive by paring down their canopies to a branch or two. Grasses die back during drought. Their new growth depends not only on precipitation from the current year, but also from previous years, so grasses may not be able to take advantage of a wet spring in one year if precipitation was below average the previous year.

Wadeable Streams

As the climate becomes hotter and drier, we expect base streamflows to decrease in wadeable streams.

Weather patterns

• Spring is coming earlier in parks across the US. One possible result is that changes in phenology (the timing of seasonal activities, such as leaf unfolding, flowering, and wildlife migration) may make some resources unavailable when they’re needed by their consumers. Parks may also experience longer fire seasons.
• Habitat for key species is changing in and around Zion National Park. Species distribution models, in combination with historical temperature data and future temperature projections, show that suitable habitat may become more abundant for Shivwits milk-vetch. Habitat may also increase for the desert tortoise but decline for American pika. Information like this can help park managers assess the potential effects of management actions.

• Overall average temperatures are rising, and they are rising faster in the Southwestern US than in some other parts of the country. At the same time, the Southwest is getting drier. Current projections indicate it will continue to get hotter. Based on that, and how vegetation has responded to previous droughts, we expect longer-and hotter-droughts that will have bigger impact on vegetation than in the past.
• It’s currently projected that by 2100, the average temperature for Moab, Utah, will be 10°F higher than it is today (66°F instead of the current 56°F). That adds up to a tremendous amount of extra heat every year. Places with an average temperature of 66°F currently include areas of the southeastern US, along with areas of southern Nevada and south-central Arizona (see the following figure)—places much warmer than today’s Moab.

• Precipitation patterns are harder to predict, but we do know that as it gets hotter, evaporation increases, meaning much more precipitation is needed to maintain the same amount of water in the system. If precipitation doesn’t come, droughts get stronger.
• Because precipitation is unlikely to increase proportionally with temperature, and because different plant communities persist under different conditions, park visitors in future decades will likely see a very different vegetative landscape. Changes to plant communities affect the animals that depend on those plants, so there may be changes across plant and animal communities.
• An expanded bimodal climate zone will have important impacts on plant communities. In western national parks, some communities are more likely to change than others.
• Even the desert can experience drought. Though they develop many adaptations to help them survive in arid environments, desert plants need certain amounts of water, and they need it at certain times.

How is the Northern Colorado Plateau Network helping park managers plan for future conditions?

In addition to improving our understanding of what’s happening and what’s likely to happen in the future, NCPN ecologists work with many partners to apply that knowledge to management scenarios. Here are some ways NCPN data can make a difference in park management.

• NCPN water and vegetation monitoring are helping to determine the sensitivity of park vital signs to a changing climate. Climate projections tell us how much change to expect. Sensitivity tells us how the things we care about are likely to respond. Combined, this tells us which, when, and where vital resources are vulnerable. Knowing this, managers can be proactive and mitigate what could happen if we did nothing but watch.
• Inventory and monitoring data are informing Climate Smart Conservation efforts at many national parks. Together, scientists and managers think through potential climate impacts to park resources, use scientific data to analyze different situations, and then identify and evaluate management options most likely to be feasible, achievable, and effective. After participating in workshops hosted by the Northern Colorado Plateau Network, parks in the NPS Southeast Utah Group are working with U.S. Geological Survey scientists to restore and conserve grasslands and pinyon-juniper forests.
• Our work is helping managers know which types of plants may be more resilient to projected climate changes. This will help them decide which plant communities to prioritize for restoration, so parks don’t waste time and money planting species that are unlikely to survive. We expect some species to be affected by drying conditions sooner than others. The more prepared we are for transitions to new vegetation assemblages, the better. If we can proactively promote desirable species, we close gaps that would otherwise be filled by opportunistic invasive (i.e., undesirable) species. Thus, we’re starting to focus on questions like, which species are best suited to the new climate on different soil types in the parks? What benefits do they offer to other species (either animal or human), and how can we maintain biodiversity? Studying how plants respond to climate across a wide area on many different soil types helps us understand our options as the climate gets drier—where and what to plant or promote, and where and what to let go.

• Linking satellite observations of vegetation condition with climate data over time can help us understand what kinds of future changes may occur. The results can help park managers know what to expect over the next few decades, providing them with time and tools to plan for a range of scenarios.
• Across the US, changes in water availability are altering which plants grow where. But not all areas experience the same climate in the same way, even within the boundaries of a single national park. A new dataset gives park managers a valuable tool for understanding why vegetation has changed and how it might change in the future under different climate-change scenarios.
• Using case studies at Zion and Bryce Canyon national parks, ecologists modeled how different fuel-reduction treatments affect post-fire hydrology. The model can help park managers estimate the effect of such efforts on wildfire severity and post-wildfire runoff or erosion. By predicting the likely results of different treatments, the model can help managers identify the most effective, cost-efficient options available to them.
• All this knowledge is made possible by the sometimes grueling task of routine long-term monitoring, which provides the essential information needed to manage parks under changing conditions.

For more information, contact Dusty Perkins (Program Manager) or Eliot Rendleman (Writer-Editor), of the Northern Colorado Plateau Network.