chapter 2: Environmental Systems

2.1 Chapter Introduction

chapter 2

Environmental Systems

Tufa towers rise out of the salty water of Mono Lake. (Dan Kosmayer/Shutterstock)

Module 4 Systems and Matter

Module 5 Energy, Flows, and Feedbacks

A Lake of Salt Water, Dust Storms, and Endangered Species

Located between the deserts of the Great Basin and the mountains of the Sierra Nevada, California’s Mono Lake is an unusual site. It is characterized by eerie towers of limestone rock known as tufa, unique animal species, glassy waters, and frequent dust storms. Mono Lake is a terminal lake, which means that water flows into it but does not flow out. As water moves through the mountains and desert soil, it picks up salt and other minerals, which it deposits in the lake. As the water evaporates, these minerals are left behind. Over time, evaporation has caused a buildup of salt concentrations so high that the lake is actually saltier than the ocean, and no fish can survive in the lake’s water.

Just when it appeared that Mono Lake would never recover, circumstances changed.

The Mono brine shrimp (Artemia monica) and the larvae of the Mono Lake alkali fly (Ephydra hians) are two of only a few animal species that can tolerate the conditions of the lake. The brine shrimp and the fly larvae consume microscopic algae, millions of tons of which grow in the lake each year. In turn, large flocks of migrating birds, such as sandpipers, gulls, and flycatchers, use the lake as a stopover, feeding on the brine shrimp and fly larvae to replenish their energy stores. The lake is an oasis on the migration route for these birds and they have come to depend on its food and water resources. The health of Mono Lake is therefore critical for many species.

In 1913, the City of Los Angeles drew up a controversial plan to redirect water away from Mono Lake and its neighbor, the larger and shallower Owens Lake. Owens Lake was diverted first, via a 359-km (223-mile) aqueduct that drew water away from the springs and streams that kept Owens Lake full. Soon, the lake began to dry up, and by the 1930s only an empty salt flat remained. Today the dry lake bed covers roughly 44,000 ha (109,000 acres). It is one of the nation’s largest sources of windblown dust, which lowers visibility in the area’s national parks. Even worse, because of the local geology, the dust contains high concentrations of arsenic, which is a major threat to human health.

In 1941, despite the environmental degradation at Owens Lake, Los Angeles extended the aqueduct to draw water from the streams feeding Mono Lake. By 1982, with less fresh water feeding the lake, its depth had decreased by half, to an average of 14 m (45 feet), and the salinity of the water had doubled to more than twice that of the ocean. The salt killed the lake’s algae and, without the algae to eat, the Mono brine shrimp also died. Most birds stayed away, and newly exposed land bridges allowed coyotes from the desert to prey on the colonies of nesting birds that remained.

However, just when it appeared that Mono Lake would never recover, circumstances changed. In 1994, after years of litigation led by the National Audubon Society and tireless work by environmentalists, the Los Angeles Department of Water and Power finally agreed to reduce the amount of water it diverted and to allow the lake to refill to about two-thirds of its historical depth. By summer 2009, lake levels had risen to just short of that goal, and the ecosystem was slowly recovering. In 2013, water levels remained close to the targeted goals. The brine shrimp are thriving, and many birds are returning to Mono Lake.

Water is a scarce resource in the Los Angeles area, and demand is particularly high. To decrease the amount of water diverted from Mono Lake, the City of Los Angeles had to reduce its water consumption. The city converted grass lawns requiring a great deal of water to native shrubs that were drought-tolerant, and it imposed new rules requiring low-flow showerheads and water-saving toilets. Through these seemingly small, but effective, measures, the inhabitants of Los Angeles were able to cut their water consumption and, in turn, protect nesting birds, Mono brine shrimp, and algae populations, and restore the Mono Lake ecosystem.

Sources:J. Kay, It’s rising and healthy, San Francisco Chronicle, July 29, 2006; Mono Lake Committee, Mono Lake (2013), http://www.monolake.org/.

The story of Mono Lake shows us that the activities of humans, the lives of other organisms, and abiotic processes in the environment are interconnected. Humans, water, animals, plants, and the desert environment all interact at Mono Lake to create a complex environmental system. The story also demonstrates a key principle of environmental science: a change in any one factor often has unexpected effects.

In Chapter 1, we learned that a system is a set of interacting components connected in such a way that a change in one part of the system affects one or more other parts of the system. The Mono Lake system is relatively small. Other complex systems exist on a much larger scale. The largest system that environmental science considers is Earth. Many of the most important current environmental issues—including human population growth and climate change—exist at the global scale. Throughout this book we will define a given system in terms of the environmental issue we are studying and the scale in which we are interested.

Organisms, nonliving matter, and energy all interact in natural systems. Taking a systems approach to an environmental issue decreases the chance of overlooking important components of that issue. Whether investigating ways to reduce pollution, increase food supplies, or find alternatives to fossil fuels, environmental scientists must have a thorough understanding of matter and energy and how these components interact within and across systems. In this chapter, we lay the foundation for the systems approach in environmental science. We will begin by exploring the properties of matter, and we will then discuss the various types of energy and how they influence and limit systems.