Climate change in the U.S. Southwest

Joshua Tree National Park is located in Southern California. In California, over 3,000 native plant species are expected to

face reductions in hospitable geographic range. Image: pixabay/public domain.

Overview

The Southwest is the hottest and driest region in the nation. It extends from the Pacific

Ocean to the Rocky Mountains and south to the Mexican border. It is home to about 56

million people. About 90 percent of these people live in cities, including Albuquerque,

Phoenix, Las Vegas, Salt Lake City, Denver, San Diego, Los Angeles, Sacramento and San

Francisco. The population is expected to increase by nearly 70 percent by mid-century.

Home to about 56 million people, the Southwest includes Nevada, Arizona, New Mexico,

Utah, Colorado and most of California.

The Southwest encompasses many different geographical features. They span from

valleys that are below sea level to mountain ranges that contain some of the highest peaks

in the United States. There are arid deserts as well as fertile agricultural land.

Climate change is affecting the Southwest. Temperatures have increased by almost 2

degrees Fahrenheit in the last century. The 2001-2010 decade was the warmest since

records began 110 years ago. Average annual temperatures are projected to rise an

additional 3.5 degrees to 9.5 degrees by the end of this century. Drought conditions are

By U.S. Environmental Protection Agency, adapted by Newsela staff on 03.31.17

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already common in the Southwest and drought periods are expected to become more

frequent and intense. They will also probably last longer. Drought will affect important

water sources, including the Colorado River Basin. Combined with expected population

growth, climate change will make existing stresses worse.

Effects On Snowpack Melt

A reliable water supply is crucial for sustaining people, agriculture, energy production and

ecosystems. The Southwest relies on the snow from mountains to melt slowly throughout

the spring and summer. This slowly melting snow is called snowpack. Snowpack also

helps keep the ground moist, which impacts the prevalence and severity of wildfires.

Over the last 50 years, there has been less snow late in the winter and the snowpack has

melted earlier. Projections indicate continued declines in snowpack in the Southwest in the

future. Less snow is falling, and higher temperatures are making it melt faster.

These images captured by NASA’s Aqua satellite show the difference between snow cover

in 2010 and 2015 across the Sierra Nevada Mountains. The snow that falls in the Sierra

Nevada provides freshwater to millions in the Southwest throughout the year. Images:

NASA/MODIS

Rapid population growth will increase the competition for water, but increased

temperatures will mean more evaporation. This will leave reservoirs and rivers with less

water.

Native American Communities Face Hardships

The Southwest is home to 182 federally recognized tribes and communities. Native

American communities face some of the highest poverty rates in the nation. They often

lack adequate food, infrastructure, transportation and access to health and community

services.

Some, including the Navajo Nation, are already experiencing the effects of drought. Many

shallow wells have run dry, which has reduced drinking water supplies. There have been

reported losses of crops and livestock used for both food and medicine.

As climate change impacts worsen, Native American populations will likely be limited in

their ability to respond to increasing hardships.

Booming Populations See Heat Stress

In the Southwest, more than 90 percent of the population live in cities. This is the highest

percentage of any U.S. region. Pavement and buildings retain heat, making cities warmer

than surrounding areas. Heat stress is already the leading cause of weather-related death

in the Southwest.

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Elderly populations and low-income households may not have access to air conditioning.

This puts them especially at risk from heat stress. High temperatures also contribute to

poor air quality, which poses a risk to people with asthma and other respiratory illnesses.

Greater energy use for cooling during heatwaves is likely to place additional strain on the

electric grid. This could result in power outages.

Wildfire Concerns In Drier Climate

Droughts, wildfires, invasive species and pests are expected to increase. They will likely

threaten native forests and other ecosystems in the Southwest. Warmer, drier conditions

have contributed to an increase in the size of wildfires in recent decades. Wildfires destroy

homes, transform ecosystems, threaten public health and damage the economy. The 2003

Grand Prix fire in southern California alone caused $1.2 billion in damages.

The distribution of plant species could also change. Approximately 40 percent of the

region is at risk of losing plants if the climate conditions are no longer tolerable for them.

Many iconic species, such the Saguaro cactus in the Sonoran Desert, are also being

threatened.

Crop Yields Shrink, Food Prices Rise

California produces more than half the nation’s high-value crops, including many types of

fruits, vegetables and nuts. Future production of these crops is likely to be affected by both

reduced water availability and rising temperatures. This will result in local economic

challenges and increasing food prices across the nation.

Over a third of the country's vegetables and two-thirds of the country's fruits and nuts are

grown in California. Irrigation systems provide water to these crops. Increasingly severe

droughts could mean that city populations and farms end up competing for water. Photo:

USDA

The majority of the Southwest utilizes irrigated croplands. As the population grows, more

freshwater may be diverted from irrigation use to urban areas. Warmer temperatures are

likely to cause crops to ripen and mature early, which is likely to reduce some crop yields.

Livestock production in the Southwest is also expected to be affected by changes in water

availability and temperatures. Pasture lands are not irrigated, which means that increasing

droughts could potentially reduce grazing lands. Meanwhile, warming temperatures

impose additional stresses on livestock.

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