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This chapter examines condensation and evaporation on Mars, with particular emphasis on how exchanges of water vapor and carbon dioxide between the atmosphere and polar ice influence the planet's climate. Both Earth and Mars have seasonal cycles. At the poles of each planet, frost accumulates during the fall and winter and evaporates during the spring and summer; and right at the poles, the frost lasts throughout the year. In these respects the seasons on Mars are like the seasons on Earth, but there are differences. For example, on Mars, there are two kinds of frost—water and carbon dioxide, the latter of which is also the major constituent of the atmosphere. The chapter first provides an overview of seasonal cycles of water and carbon dioxide on Mars before discussing the effect of winds on weather. It also considers dust storms and weather fluctuations on Mars.

This chapter examines how the Middle West recovered from the ill effects of the Great Depression. The Great Depression was something Americans hoped they would never experience again. In the rural Midwest, foreclosures and sheriff's auctions were common. The worst drought years devastated the land. Dust storms blew with such intensity that crops failed and machinery broke down. World War II sparked the economy, revived agriculture, and coincided with better weather. However, the war took millions of men and women away from their families, necessitated mandatory rationing, and drove up prices. When it was over, rural communities faced continuing challenges. The chapter considers the case of Smith Center, Kansas, to illustrate the challenges rural communities faced as they overcame the setbacks of the Great Depression and prepared for the era ahead. Recovery from the Great Depression varied across middle America, but many of the dynamics evident in Smith County occurred elsewhere.

This introductory chapter provides a background of the 1930s Dust Bowl on the U.S. southern plains, where the ancient grasslands that protected the soil from prairie winds and rains and nourished regional species were destroyed within just a few decades, following the violent opening of the plains to white settlement and the global market in the 1800s. Under pressure from the vagaries of the world economy, settlers sheared the land to expand cash-crop agriculture and ranching. As major drought descended on the plains, winds and static electricity lifted the desiccated, exposed topsoil, forming dust storms on an unprecedented scale. Such massive loss of soil and continued dry conditions meant the land could no longer support life as it once had. By the end of the 1930s, tens of thousands of people were displaced. Hence, when scientists today predict the increasing possibility of Dust Bowl-like conditions, they are signaling a particular kind of extreme ecological and social change.

Changes in the land itself are the subjects of chapter five. The first section which considers contemporary debates over the causes of different types of soil erosion, in particular drifting sands, dust storms, similar to those on the Great Plains during the Dust Bowl, and the growth of ravines and gullies. The chapter moves on to consider debates over whether the steppes were drying out and the water table falling, and whether the fertile black earth was becoming exhausted. By the time of the drought and harvest failure of 1891 there were growing concerns about desertification. By the end of the period, most specialists agreed that human activity had greatly exacerbated these changes. All the changes in the environment considered in part II were detrimental to arable farming on the steppes.

In this conclusion, the author reemphasizes arguments made within the preceding chapters. The Green Depression argues that depression-era American literature (and some films) depict ideas that would become associated with environmentalism in the second half of the twentieth century. She focuses on authors from the period whose work echoes changes in conservationist thought, in three areas in particular. Witnessing the severity of the period’s dust storms, widespread flooding, and use of atom bombs, depression-era authors began to more fully articulate the apocalyptic effects that humans can have on the environment. The conclusion highlights other questions that suggest the abundance of further work that can (and should) be done on the role of environmentalist thought in cultural works of the period.

When the last great North American frontier, the Great Plains, closed three decades into the twentieth century, farmers could no longer replace the exhausted soils on their farms with fertile, uncultivated lands elsewhere. The closing of the frontier caged American farmers. The fall in the prices of agricultural products after World War I, coupled with widespread soil exhaustion, deepened rural poverty during the 1920s. The Depression impoverished rural peoples even further, and it discredited the capitalist class. In a political-economic sense, the Depression leveled some elements of inequality. The Dust Storms of the mid-1930s provided graphic, visual evidence of environmental degradation on farms, and they focused popular attention on the need for more sustainable practices. Franklin D. Roosevelt responded, with support from the large New Deal coalition, pushing through reforms in soil conservation and forest restoration that have shaped natural resource practices in the United States for almost a century.

A third attempt by the JPL–Oxford partnership to make meteorological observations of Mars was successful at last. Their newest instrument, Mars Climate Sounder, reached the Red Planet on Mars Reconnaissance Orbiter and started taking wonderful data. Temperatures, clouds, and dust were mapped over several Martian years and the data fed into a computer model, previously used for weather forecasts on Earth, to try to understand Martian phenomena such as global dust storms. As well as comparing the meteorology on Earth and Mars, they were trying to understand how and why the climate on Mars, once warm and wet and suitable for life, had changed to a frozen desert.

In coastal dune systems, plant communities are fundamentally the product of interaction between disturbance of the substrate, impact of high wind velocities, salt spray episodes, sand accretion levels and other factors of the environmental complex. Burial by sand is probably the most important physical stress that alters species diversity by eliminating disturbance-prone species (Maun 1998). There is a close correlation between sand movement and species composition, coverage and density (Moreno-Casasola 1986; Perumal 1994; Martínez et al. 2001). Sand accretion kills intolerant species, reduces the relative abundance of less tolerant species and increases the abundance of tolerant species. It filters out species as the level of burial starts to exceed their levels of tolerance. For example, lichens and mosses are the first to be eliminated, then the annuals and biennials and finally the herbaceous and woody perennials. Again within each life form and genus there are significant differences in survivability. Burial imposes a strong stress on production by altering normal growth conditions and exposing plants to extreme physiological limits of tolerance. Do plant communities occurring in different locations within a dune system correspond to the amount of sand deposition? Several studies (Birse et al. 1957; Moreno- Casasola 1986; Perumal 1994) show that the species composition and their distribution are strongly related to the long-term average sand deposition. The evolution of a plant community in coastal foredunes requires frequent and persistent predictable burial events specific to a particular coast. In a large majority of sea coasts burial occurrences are of relatively low magnitude and species occupying the coasts are well adapted to withstand the stress imposed by burial. This recurring event within the generation times of plant species allows them to acquire genes of resistance over time and evolution of adaptations to live in this habitat. A prerequisite to survive in this habitat happens to be the ability to withstand partial inundation by sand. To survive the dynamic substrate movement a plant species must be a perennial, be able to withstand burial, endure xerophytic environment, spread radially and vertically, and adapt to exposure on deflation and coverage on burial (Cowles 1899).