Southern Regional Water Program

Research, Extension & Education Water Quality Programs through the Land Grant University System

Environmental Restoration In New Mexico

In New Mexico, trees grow along waterways at all elevations and in the mountains and foothills where precipitation is adequate. Juniper savannahs appear where annual precipitation reaches 10 inches annually. As rainfall increases with elevation, pinyon woodlands replace juniper. Ponderosa pine forests begin to occur where rainfall exceeds 15 inches annually and forest types gradually change to mixed conifer and finally to spruce-fir forest types at the highest, wettest elevations. New Mexico’s forests are valued for habitat, recreation, wood products and sheltering the watershed.

Today’s forests have changed considerably from what European settlers described pines.jpgduring the late 1800’s and early 1900’s especially in the lower elevation forest zones. Most historical writings describe the condition of ponderosa pine forests as much more open than we see today. Early forest inventories from southwestern ponderosa pine stands indicated an average of 20-40 trees per acre with a fairly even distribution of small to large trees. Trees occurred in groups of similar size and there was considerably more grass and fewer understory trees than we see on many forest sites today. Today’s forests often have hundreds of trees per acre, smaller average diameters, dense cluttered understories and little grass.

Changed forest conditions are believed to be a result of a change in fire frequency and behavior due to past unregulated grazing, careless logging and fire suppression. By studying tree rings and fire scars on old trees and stumps, forest scientists have determined that before the turn of the last century, low intensity fires burned through the grass in ponderosa pine forests every 2-10 years and in the pinyon-juniper woodlands every 10-30 years. These fires left some groups of smaller trees and burned up others. The thick bark of old ponderosa pines was scarred but the trees were not killed. Thus groves of trees were kept open and park like. When eastern settlers began to arrive in New Mexico in large numbers in the 1870’s after the Civil War, they brought with them huge numbers of cattle and sheep and overgrazed the grasses. Lightening-started fires no longer had a grassy fuel to carry them. With settlement came a demand for building materials and railroad ties and many of the trees over 9 inches in diameter were cut. Only the best wood was taken and the treetops and heavy branches were left behind. When these caught fire, the fires were hot and destructive. In response, a policy to put out all fires as soon as possible was implemented and was one of the early missions of the Forest Service, which was started in 1905.

Forest Conditions Today

Over time the forest regenerated without the low intensity grass fires that had once thinned the young trees. As the trees grow, forest density continues to increase. This has had an impact on stream flow, forest ecology, fire behavior and water quality.

USDA Forest Service researchers have documented the effects of dense forests on stream flow. Low flows have gotten lower and intermittent streams dry up sooner. Low flows affect water temperature, which affects fish and other aquatic life. Increases in stream flow have been found after logging, forest thinning and prescribed fire. Following a reduction in forest density, streams are now flowing that had not flowed in years.

As pine forests became denser, shade tolerant conifers like white fir became established beneath them. Mixed conifer forest increased and moved onto sites formerly dominated by ponderosa pine and aspen. Crowded forest conditions and changes in distribution of tree species in New Mexico have led to increases in certain forest insects and diseases. Trees under stress are more vulnerable to attack by wood and bark boring insects and more severely damaged by other insects and diseases. Trees in crowded conditions mature at smaller diameters and cannot provide some of the ecological benefits of larger diameter trees. Larger trees provide long-lasting habitat for tree dwelling wildlife. Larger trees continue to provide benefits smaller trees cannot even after they have died and fallen. Large fallen trees can provide habitat, hold moisture, reduce soil erosion, and allow other vegetation to become established. They can survive ground fires that would consume smaller logs and continue to provide benefits for decades in dry environments.

Today’s dense forests burn much differently than the open forests of our past. Fires burn less often but they burn over larger areas and are more destructive. Dense vegetation carries fires to the tops of the trees where it spreads through treetops rather than along the ground, killing even large, thick barked trees. High intensity fires consume the duff layer and contribute to rapid soil erosion and run off into waterways. Forest Service studies have found that following intense forest fires, soils become repellent to water and erosion increases.

What Needs to be Done?

Thinning, prescribed fire and timber harvests can all be used to reduce forest density, increase productivity and reduce risk from wildfire.

Resources and Programs

New Mexico State University has established programs designed to provide environmental restoration assistance. Below are some key links to information and resources available to assist you.

Extension Outreach

NMSU Cooperative Extension Service through the Cooperative Forest Health Program with the New Mexico Forestry Division works with private landowners to improve forest health conditions. Through educational publications, workshops, and on site evaluations, landowners receive information on how to better manage their forests and minimize environmental impacts. Aerial surveys are conducted each year over 1.5 million acres of State and private forestlands to locate insect and disease outbreaks. This information is used in making forest management decisions and salvaging timber. Forest homeowners are also taught how to reduce their risk from wildfire by improving defensible space around homes, using non-combustible building materials and planting less flammable landscape plants.

NMSU Cooperative Extension Service also supports and helps coordinate New Mexico Forestry Camp, a weeklong educational camp for teenagers sponsored by the Cuba Soil and Water Conservation District.


NMSU’s Mora Research Station is dedicated to forest science research and runs a forestry genetics program, supports the State’s seedling program, leads in high elevation mine reclamation work and is studying carbon sequestration in semi-arid ecosystems.

College and University Education

Youth and continuing adult education are critical to develop new talent and human resources to address the water quality issues of the future. Educational curricula in environmental restoration are available within several departments at New Mexico State University. Key departments include:

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