Natural Resources Monitoring at Chiricahua National Monument

Overview

Chiricahua National Monument was established in 1924, to protect its rock "hoodoos" that rise hundreds of feet into the air. Another important natural feature, especially for the park's plants and animals, is water. The monument contains all or parts of five major watersheds in the northern Chiricahua Mountains, as well as a wetland marsh. Rich in diversity, the monument boasts many plant communities, including grasslands, deciduous and evergreen forests, and scrublands.

The monument lies east of the Sonoran Desert, in a region called the Apache Highlands. The Apache Highlands are characterized by mountain "sky islands" separated by grassland and desert scrub "seas." This location, at a biogeographic transition point between the Sonoran and Chihuahuan deserts on the east and west, and the Rocky Mountains and Sierra Madre to the north and south, is reflected in the park's diverse flora and fauna.

Leading natural resource issues include colonization by invasive exotic plants, altered fire regimes, and the consequences of climate change.

The Sonoran Desert Network monitors air quality, climate, groundwater, invasive exotic plants, landbirds, springs, seeps, and tinajas, terrestrial wildlife, and vegetation and soils at Chiricahua National Monument. The results of this work can be found in a variety of publications and other information. The network also maintains species lists for the park.

Park Setting and Key Resources

Biogeography and physiography

Chiricahua National Monument is located near the confluence of three major ecoregions in the American Southwest: the Apache Highlands, Chihuahuan Desert, and Arizona–New Mexico Mountains. The monument's location at this biogeographic transition point is reflected in the diverse flora and fauna monitored by the Sonoran Desert Network. The park lies in a region called the Apache Highlands. The Apache Highlands are characterized by mountain "sky islands" separated by grassland and desert scrub "seas."

One of the higher-elevation network parks, Chiricahua National Monument includes three biomes: Madrean evergreen woodland, interspersed with interior chaparral and temperate forest. Average annual precipitation is 19.4 inches (494 mm).

Local geology and soils

The monument was set aside for the unique rock pinnacles, or "hoodoos," that are most common in its central and eastern portions. Hoodoos are erosional features formed in the Rhyolite Canyon Tuff, which accumulated in large quantities following three massive volcanic eruptions about 26.9 million years ago. Evidence of this dynamic geologic past is found throughout Chiricahua National Monument. The park also includes late Paleozoic, Permian limestone that is an order of magnitude older than the more evident and iconic volcanic features. Upland soils within the park are generally shallow and rocky. Soils are relatively deep along the canyon bottoms.

Climate

Chiricahua National Monument experiences climate typical of the Apache Highlands ecoregion: highly variable, bimodal precipitation with a considerable range in daily and seasonal air temperature, and relatively high potential evapotranspiration rates. Approximately two-thirds of annual precipitation falls during summer thunderstorms, where maximum air temperatures often approach 86°F and lead to violent (and often localized) rainstorms. The bulk of the remaining annual precipitation falls in relatively gentle cool-season events of broad extent, often as snow. Winters are often cold compared to many other Sonoran Desert Network parks. Maximum and minimum average air temperatures were generally comparable to 30-year normals, although mid-summer maximum average air temperatures were slightly higher from 2002 to 2010.

Weather and climate data for Chiricahua National Monument and all other Sonoran Desert Network parks can be found at The Climate Analyzer, an interactive website that allows users to create custom graphs and tables from historical and current weather-station data. A weather and climate inventory was created for the Sonoran Desert Network in 2007. A more recent brief shows the magnitude and direction of ongoing changes in climate at Chiricahua National Monument.

Key Issues

Invasive exotic plants

Biological invasions into new regions have increased at unprecedented rates in the past few hundred years. Once established, non-native plant species often lead to changes in ecosystem processes that in turn lead to functional and compositional change. In the American Southwest, historic and current land-management activities, such as livestock grazing and fire suppression, are thought to have helped make arid lands more vulnerable to invasion and subsequent loss of native species and biodiversity.

Vegetation research at Chiricahua National Monument has documented a total of 61 non-native species, which is approximately 6% of the monument's known flora. Many of the non-native species are ornamental, garden, or forage plants associated with the Faraway Ranch Historic District.

Major concerns include the annual herb, Malta starthistle (Centaurea melitensis), and the South African perennial bunchgrass, buffelgrass (Pennisetum ciliare). This exotic has developed new, more cold-hardy strains and is expected to flourish under the warmer temperatures likely to be associated with climate change. Park management has also made Lehmann lovegrass (Eragrostis lehmanniana) a priority for management.

Altered fire regimes

Several tree-ring studies of historic fire occurrence in and around the monument exhibit a pattern similar to that of most of the American Southwest: relatively frequent ground fire until the late 19th century, when extensive fire suppression activities and the onset of livestock grazing greatly limited the occurrence and extent of wildfire. The result was the absence of widespread fire at the monument from 1886 until the Horseshoe II Fire of 2011. Effective fire suppression had important consequences for the Chiricahua landscape. Repeat aerial photography (1935 vs. 1993) and field plots have documented dramatic increases in woody plant cover, particularly that of fire-sensitive trees, such as border pinyon pine (Pinus discolor). The Sonoran Desert Network is helping to document post-fire vegetation conditions at the park.

The consequences of climate change

Although there is a near consensus amongst scientists regarding the occurrence, causes, mechanisms, and broad-scale ecological consequences of global climate change, rates and patterns at finer spatial and temporal scales can be challenging to predict. However, as science and society increasingly focus on climate change and its consequences for ecosystems and human civilization, our understanding of these impacts is improving.

It has been predicted, with high or medium-high confidence, that the Southwestern U.S. will sustain increased drought and heat extremes, and decreased available water resources, due to climate change. Positive feedback cycles with drought, fire, and insect outbreaks are forecast, as are increased occurrence of extreme weather events.