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CHAPTER 1
Natural History of a Forgotten American Grassland
We left the magnificent savanna and its delightful groves, passing through a level, open, airy pine forest, the stately trees scatteringly planted by nature, arising straight and erect from the green carpet, embellished with various grasses and flowering plants.
William Bartram (1774, near present-day Gainesville, Florida)
Taking a break from after-dinner email, I stroll into the family room, glass of cabernet in hand, to find my family watching the Discovery Channel on TV. I almost never watch television, so I do not know what to expect when I encounter one of these strange machines. This time I see a view from a low-flying aircraft of a beautiful green prairie landscape somewhere in the Great Plains of North America. The low undulating hills and soft, waving grass roll into the distant horizon. It is an inviting and comforting sight, a verdant scene once common in the center of our continent but now hard to find due to conversion of millions of acres of prairie to agriculture. The narrator, a well-known actress who, my daughter informs me, has battled aliens in movies, repeats a well-worn refrain: âGrasslands occur where there is too much rain for desert, but not enough rain to support forest.â
I hurry back to my computer to capture that quote, which can be found in various forms in countless textbooks. In a 1991 book series on ecosystems of the world, R.T. Coupland states that grasslands âoccur along a climatic gradient between desert and forest.â A textbook of biogeography by Mark Lomolino and coauthors declares that âtemperate grasslands are situated both geographically and climatically between the deserts and the temperate forestsâ (fig. 1.1). These statements epitomize the paradox of grasslands in the rainy southeastern United States: few people, even ecologists, know they exist or expect them to be here. The South has more than enough rain to support forest. Whether a particular landscape in the South supports forest or grassland depends on factors other than precipitationâespecially fireâbut also soils, herbivores, and other influences. Ecologists describe this phenomenon as âalternative stable states.â Grassland was a common or dominant alternative state across much of the South, but that fact has been largely forgotten.
When educated people in North America hear the terms grassland or prairie, most of them visualize the Great Plainsâthe scene I saw on television. Here, grassland dominated a vast region or biome. Grassland is the largest of the four major biomes on earth and the largest in North America, covering some 300 million hectares (ca. 750 million acres) before European settlement. (Note: I use English units in this book for the benefit of the general reader, but provide conversions from metric to English, as appropriate, where metric units are used in original sources.) The grassland biome (including savannas, which are grasslands with scattered trees) covers more than 40 percent of the land surface of the earth and is inhabited by more people than any other biome.
Mean Annual Precipitation (cm)
Figure 1.1. A climograph showing biome-scale relationships between climate and vegetation. Grassland/savanna is shaded. Grasslands in the southeastern United States do not follow this pattern of being intermediate between desert and forest. Adapted from Lomolino et al. (2006) after Whittaker (1975).
The climate of the South (fig. 1.2) varies greatly with latitude, longitude, and elevation, but none of it matches the traditional description of the grassland biome. Whereas most of the grassland biome of North America receives well under forty inches of rain per year, the South gets about forty-eight to eighty inches. The climate, except at high elevations, is humid-temperate to warm-temperate from the Ohio Valley south to approximately the northern Florida Peninsula and Gulf of Mexico. Florida has a steep climatic gradient, with average temperature increasing rapidly with decreasing latitude. Northern Florida experiences regular freezes in winter; freezes decline sharply in frequency southward. South Florida is protected by the Gulf Stream, which originates as warm water from the tropical North Atlantic. Many biogeographic classifications designate south Florida as tropical, consistent with the dominance of south Florida (especially the Keys) by Antillean species. The climatic and physiographic diversity of the South partially explains the high species richness found in southern grasslands, but there is much more to it than that, as this book will explore.
Figure 1.2. The study area, defined to encompass a variety of grasslands with southern (and often western) affinities. This entire region of the southeastern United States is referred to as âthe Southâ in this book. âSoutheastâ and âsoutheasternâ are used, where applicable, for the region east of the Mississippi River and to contrast this region with the southwestern and south-central United States.
NATURAL HISTORY FOR CONSERVATION
This book is about grasslands of the South, but it explores a bigger topic: how knowledge and practice of natural history are essential to the conservation of biological diversity. The logic is straightforward: to conserve wild living things and their habitats, we must know them and understand how they live and interact. Recognizing a species by name is essential to learning more; hence, it is deplorable that training in taxonomy is plummeting. Consider this example: Antje Ahrends and coauthors, in a paper called âConservation and the botanist effect,â show through a study of plant records from Tanzania that botanists with proper training in plant identification record more species (20 more species per 250 specimens) and more endemics (narrowly distributed species) and other taxa of conservation concern than botanists with inferior taxonomic skills. Poor training in natural history inevitably leads to second-rate conservation.
Natural history in the broad sense is not just identifying and naming things; it incorporates and intertwines biogeography, ecology, evolutionary biology, anatomy, physiology, taxonomy, systematics, paleontology, environmental history, geography, anthropology, archaeology, and other subjects, but with a focus on whole organisms and communities. What distinguishes natural history from most of current academic science is not just its acceptance of observation as a complement to experimentation, its rejection of extreme reductionism and hyperspecialization, or that much of it must be learned outdoors. More essentially, natural history insists on intimate familiarity with some aspect of biological diversity. A naturalist can be a generalist (familiar with many groups of organisms or types of ecosystems) or a specialist (highly knowledgeable about one or a few groups or places)âwe need both. Perhaps the ideal naturalist has broad knowledge complemented by specialized expertise on a particular taxonomic group or subject. The great ant biologist, all-round naturalist, and living legend Ed Wilson comes to mind, as does the generalist Charles Darwin with his special interest in barnacles, orchids, and earthworms, among other groups.
A modern tragedy is that we are losing naturalists as the old ones die off or retire and few new recruits are trained or hired. Schools and universities are eliminating field trips and field-based courses. At the same timeâand the two trends are connectedâmajor conservation organizations have shifted away from natural history and even from protecting biodiversity as a primary goal. Instead, they have moved into the vaguely defined territory of âecosystem services,â where nature is valued for its functional and economic services to human society, not for its beauty, fascinating peculiarities, or inherent dignity. This trend worries me, because a society that values nature only for its blunt utilitarian worth is not likely to care much about the extinction of species or the loss and degradation of natural communities that offer no tangible services. As extinction rates increase, so does the urgency of restoring natural history to its rightful place in science and conservationâat least on a par with concern for ecosystem services. Biodiversity and ecosystem services are complementary and should not be placed in competition with each other on the conservation agenda.
Beyond its importance for conservation, natural history provides a way for people to feel at home. Nothing alarms me more than someone who has no clue about what watershed she lives in and cannot name even five or ten species of plants and animals in her neighborhood. Such lack of awareness signals a pathological disconnection from nature. We need to know our nonhuman neighbors and come to see them as friends. Learning about the geologic history, flora, and fauna of the place we live in helps us feel that we belong here, regardless of our socioeconomic status, race, ethnicity, or whether or not we were born and raised in this place. Natural history is democraticâanyone can practice itâand it opens up limitless opportunities for joyful experiences. These experiences then circle back to conservation. We become more eager to save plants, animals, and places when they are familiar rather than strangers.
This book is a journey driven by curiosity, which is what being a naturalist is all about. From my first exposure to southern grasslands, I wondered why these places are so scarce in trees, whereas often adjacent to them are dense forests or swamps. As a beginning graduate student I learned that the pine savannas I viewed on field trips to Florida were the prevailing vegetation type of the Coastal Plain until quite recently. I did not yet know that the mixed hardwood forests I saw through the car windows as a child during family trips to Florida, forests which now dominate much of the âundevelopedâ parts of the region, are for the most part artifacts of fire exclusion or former agriculture. Many trained ecologists do not know this.
Years later, while researching the status of endangered ecosystems across the United States, I discovered that grasslands are, in general, the most imperiled of all terrestrial ecosystems in the country. This is especially true when endangerment is measured as extent of decline since European settlement, but is also often true in terms of present and future threat. Some of these grassland ecosystems dominated entire physiographic regions, such as the Coastal Plain, Great Plains, and Palouse, whereas others, such as in the Appalachians, Midwest, and Northeast, occurred as relatively small patches in a matrix of dissimilar vegetation, usually forest. Learning about the plight of grasslands, I pledged to do what I could to protect them and help them recover their former glory. Such is the moral responsibility of a naturalist.
GRASSLANDS IN THE SOUTH?
I regularly meet professional ecologists, including some southerners, who give me a puzzled look when I mention that I am writing a book on southern grasslands. The lack of awareness of native grasslands in the South represents a case of collective amnesia. A few human generations ago, grasslands were abundant across much of the South; today they are rare. Driving through the region today, one mostly sees agricultural fields, pine plantations, dense and mostly young hardwood forests and swamps, and, increasingly, urban sprawl. One has to know where to go to find remnant southern grasslands. If you find one, you might be surprisedâa few still cover tens of thousands of acres.
I am fortunate to live in Florida where, amazing...
