Forgotten but not gone

Forgotten Grasslands of the South. Natural History and Conservation by Reed F. Noss. Island Press 2013

Walden Warming by Richard Primack. University of Chicago Press 2014

Reading Noss’s work, I recall Faulkner’s words, “The past isn’t gone. It isn’t even past.” Forgotten, neglected, tragically diminished, but not gone. Noss describes his travels to visit what was once a vast archipelago of grass-dominated ecological communities, ranging from endless longleaf pine savannas (see my post on Looking for Longleaf) to tiny rock outcrop barrens. This island landscape stretched across the southeastern United States from Texas to Virginia. In fact, though Noss does not discuss them, these communities are found up into the mid-Atlantic and New England. Today, the remaining islands, in a sea of agriculture, industrial forestry and urbanization  only hint at what has vanished beneath the waves of “progress.” But remarkably, there is enough to form the core of a restored landscape, something that will be a major challenge for 21st century ecologists.

Many types of habitats fit under the term “grassland.” Woodlands have trees, but their crowns cover less than three-fourths of the ground, allowing herbaceous plants, especially grasses, to thrive. Savannas have scattered trees, with less than about fifty percent cover. Meadows, glades, barrens and balds have only isolated patches of trees. Noss also describes plant and animal species endemic to the southeastern grasslands. An endemic is a kind of organism found in a particular type of community or a local area, and nowhere else. Many of these are critically imperiled, occurring today at only one or two places. The book is illustrated with his photos of the communities and the rare plants.

Noss has really interesting things to say about the factors that have maintained open, grass-dominated habitats over ecological and evolutionary time. The main ecological question is: what is preventing tall woody plants from taking over? The climate is warm enough, and rainfall is adequate for trees. It could be lack of a deep, firm soil that roots can penetrate to support tall stems. It could be that the soil stays wet or dry too much of the year. It could be constant disturbance by flood, wind, fire or herbivores. It could be lack of sufficient nutrients to support trees and shrubs. At any particular site, it’s most likely a combination of two or more of these factors.

The evolutionary question is: how have the species that comprise these ecological communities arisen and survived in a dynamic landscape? The answers are tentative and complicated, especially those related to changing climate. The distinctiveness and diversity of the endemic species, especially their adaptations to fire, imply a long evolutionary history. Some of the endemic plant species, such as those in certain rock outcrop barrens, may have evolved recently, while others, like the ones in the longleaf pine savannas, have been around for a very long time. This field of research is called phylogeography because it looks both at phylogenetic (evolutionary) relations among different populations and species and at the geographic patterns of climate (and so, the species’ habitats) now and in the past.

Many authors have stated the grasslands originated only as a result of disturbance by humans, who do not seem to have reached America before 30,000 years ago at the very earliest. If the grasslands originated before the Pleistocene ice ages, how did they survive the periods of peak glaciation and cold? Noss cites pollen data to show that most of the southeast had a cool temperate climate during the ice ages, but evidence from geomorphology suggests that there were periods of boreal conditions with deep seasonal frost or even permafrost. Aeolian landforms, created by strong winds coming off the glaciers, include dune fields, sand sheets and the famous Carolina bays. These indicate that there were periods where there was little vegetation to stabilize the surface. One possibility is that the pollen record is incomplete, because the intervals without vegetation produce essentially no pollen. Another is that, if the Gulf Stream stopped during the coldest intervals, the Gulf of Mexico would have been a tremendous heat reservoir, keeping the coastal areas warm, while inland sites were cold. On maps of the ice age drop in sea level, the additional dry land, just on the west side of peninsular Florida, looks nearly as large as North Carolina. Thus, a lot of grassland species might have retreated there.

Noss’s book and a recent article (Noss, R. F., Platt, W. J., Sorrie, B. A., Weakley, A. S., Means, D. B., Costanza, J. and Peet, R. K. 2015. How global biodiversity hotspots may go unrecognized: lessons from the North American Coastal Plain. Diversity and Distributions 21: 236–244), which includes the coastal plain up to Cape Cod, call the region a biodiversity hotspot. This is based on the great numbers of plant, vertebrate and insect species in the region and the number of those species that are endemic to it.

The article calls for the North American Coastal Plain to be listed as a global biodiversity hotspot. A colleague who studies southern grasshoppers told me that the group behind the effort to achieve listing had several more papers in the pipeline that they expected would be needed to convince the Critical Ecosystem Partnership Fund to add the NACP as hotspot number 36 They succeeded on the first try, just after the article was published ( Hooray!

Now the hard work begins: convincing people, especially government officials and private conservation groups, to take action. Here in New Jersey, most conservationists still see the coastal plain as a forest region. Natural enough, since fire suppression for the last eighty years has effectively converted what were once woodlands and savannas into dense forests of pine and oak trees and huckleberry shrubs. “Forest,” has such cultural significance in American environmentalism that it is very difficult to convince anyone that this is not what Nature intends. Add modifiers like “old growth,” “pristine,” “climax,” and you have idols that it is very hard to get environmentalists to stop worshipping.

Most people I know in the Mid-Atlantic region tend to blame “development” for loss of natural habitats. To an extent, this is true for the grasslands of the South, especially the loss in recent times of the smaller glades and barrens, but other factors are historically more important. Noss mentioned drainage and conversion to farmland, but this applies mainly to the wetter, richer grasslands. Dense tree plantations have replaced pine savannas. Another factor is loss of large herbivores, beginning with the extinction of much of North America’s megafauna – mammoths, ground sloths, etc. – around 15,000 years ago. To some degree, cattle, hogs and sheep may have supplied their place in the early post-1492 times of open ranges and even today, but livestock can do more harm than good to natural habitats, and they will never be allowed to recreate the vast network of “buffalo traces,” leading to salt licks and waterholes. These trails provided habitat and dispersal routes for grassland plants, as roadsides do today, if we don’t mow them in the growing season or allow exotic invasives to take over.

By far the clearest factor reducing grasslands is fire suppression. Since the advent of motorized firefighting in the mid-twentieth century, the number of fires has changed little, but the area burned annually has greatly decreased ( This means that fire return intervals have generally become too long to prevent establishment of closed forest canopies. This is fine if you want to grow trees for wood or fiber but terrible for the plants and animals of woodlands, savannas and grasslands.

I have tried for years to convince my friends in the New Jersey Pine Barrens that the greatly increased plant canopy cover since fire suppression began to be effective has caused much of the reported drying out of the landscape. They prefer to blame the loss of wetlands and headwater streams on wells drilled by farmers, developers and casinos sucking water out of the ground. Trees and shrubs are taking just as much water through their roots and evaporating it through leaves, 300-500 pounds of water for every pound of sugar they make in photosynthesis. Some of my conservationist friends and colleagues oppose even moderate thinning of trees in the Pine Barrens. They talk about endangered species’ need for undisturbed habitat, not recognizing that on the coastal plain, far more species are threatened by the loss of open land with herbaceous vegetation – grasslands, woodlands, savannas and meadows. A very experienced botanist I know, however, has become convinced, after seeing species like pine barrens gentian and turkey beard springing up in the wake of forest thinning and reintroduction of fire on managed lands. Too bad the New Jersey Forest Service officials still thinks Smoky the Bear has the last word. They are courting disaster as fuel loads continue to build up in the pines, but they won’t believe that a fire could occur that they could not control. This is incredibly short sighted.

I also wish our environmental community would back off its opposition to natural gas pipelines, which actually create open habitats, and devote more of their resources to stopping the motorized mayhem that’s destroying the last of our native savannas and sand ridge communities all across southern New Jersey. In the Pinelands National Reserve, motorized recreation is not a permitted land use, but pressure from the motorheads has prevented meaningful regulation or enforcement.

Besides these immediate threats, I wonder whether the coastal plain biodiversity hotspot can survive climate change. As shown by Richard Primack in his excellent book, Walden Warming (Chicago 2014) there are already substantial changes in the flora and fauna of New England since Thoreau kept a naturalist’s journal in the 1850’s. Surely, though we lack clear evidence, such changes are occurring in the North American Coastal Plain. For plant populations to persist, they must either acclimate (adjust their flowering and fruiting physiology) adapt locally (through natural selection of individuals that best match the warmer climate) or disperse their seeds northwards. Primack points out that the barriers created by towns, farms and highways make it difficult for native plants to disperse to suitable new habitat.

A look at the map of the coastal plain shows another problem: the northward narrowing of the geologic region, until it peters out at Cape Cod and in the sandy outwash plans of southern New England. Even if species can shift northwards, they will find themselves funneled into increasingly tight confines, reduced even more by sea level rise. Europe’s flora is impoverished compared to its temperate counterparts in North America and Asia, because southward dispersal during the height of the last ice ages ran into the barrier of the Alps. The coastal plain’s denizens may be similarly crushed against the rock ribs of New England.

Noss’s points out that many people feel that preserving nature for its own sake is as important as preserving it for its benefits to us. He recasts Jack Kennedy’s famous dictum as, “ask not just what nature can do for us, but also what we can do for nature.” He estimates that temperate grasslands have the lowest ratio of lands preserved to lands destroyed of any major ecological system on earth. In the North American Coastal Plain this ratio may be even lower, although perhaps with more prospect for restoration than in some areas, because so much has been lost to fire suppression, which is fixable.

Noss is a strong proponent of saving all that we can in whatever ways are effective. He is against any form of ” triage,” writing off of species and communities that we decide in advance can’t be saved. He also criticizes the Nature Conservancy for overemphasizing what they call “working landscapes,” and neglecting the smaller, uneconomical bits, those tiny glades, barrens and rock outcrops that house such amazing numbers of endemic taxa. Noss argues we need to practice preservation on many scales, beginning with a ban on development of any new natural lands. We should be redeveloping abandoned or underutilized sites, close to existing development. I agree, but we need to find some way to effectively transfer development rights, or landowners will block any such policy. He also argues that we need to change the policies and practices of our state and federal agencies and private conservation groups to better manage lands already protected. Too many of the best areas are either over-utilized or neglected.

Both these books are excellent reads, especially the authors’ descriptions of work in the field with their colleagues and collaborators. One gets a sense that there are a lot of very dedicated ecologists working to preserve biodiversity in our changing landscape and changing climate. One of the encouraging developments I have noticed is the great increase in contributions from what are now called, “citizen scientists.” People, who might once have pursued their love of plants, birds or butterflies in isolation, now contribute to both current data collection and preservation of valuable old data (Thoreau’s Journals are a prime example) through projects like iDigBio. More could be done, especially if there were a way to report and then evaluate outliers: unusual sightings, anomalous individuals and things in the wrong place at the wrong time. Where economic interests are involved, we do usually follow up, as with introduced pests, but otherwise many valuable observations in our rapidly changing environment may be written off as misidentifications or just lost. I would like to see more naturalist’s, especially our large crop of butterfly watchers learn when and how to collect proper specimens to verify their unexpected sightings. Scientific collecting is almost never a threat to populations of insects, and a specimen allows positive identification and preservation of a record in a way photographs can’t.

I would strongly recommend these two books to anyone concerned about the future of biodiversity along our Atlantic coast.

New world history

A Natural History of the New World. Ecology and Evolution of Plants in the Americas, by Alan Graham. 2011. Chicago. University of Chicago Press. 387 pp.
This is an ecological and evolutionary story acted on the stage of two continents from the close of the Mesozoic to the recent. South America starts out isolated or nearly so, while North America begins joined to Eurasia across the proto-Atlantic. It ends with two continents joined by a narrow isthmus and a sporadic connection to Siberia across the Bering Sea. During this time as the Americas override the Pacific plates, a series of great mountain ranges form along the western edges of both continents, altering the directions of rivers and radically altering the climate of the continental interiors. Late in the period, the shift towards glacial climates turns what were temperate climates under a polar insolation regime into boreal forest and tundra, with deciduous forests to the south and new dry ecosystems in the arid west.
It is a dramatic story, with a shifting cast of characters, most impressively the higher angiosperms and the radiating mammals responding to each other as well as struggling among themselves to dominate under the shifting conditions. The rise of groups like the grasses and the ungulates with their associated carnivores are among the most visible and dramatic developments, if not quantitatively as significant as the insects and fungi, which changed much less over the same time. This is a vexed question; megafauna and keystone species enthusiasts on the side of top-down regulation and ecosystem engineering, those of us who look at energy flux and nutrient cycles as keys to ecological processes and who see microbes as the dominant force, alongside plants, on the bottom-up side. Probably both views are right some of the time. No doubt, though, that climate and geology – lithosphere, atmosphere, hydrosphere – are the ultimate regulators, although the biosphere’s impact on carbon cycling is also significant.
This is a very detailed book, giving an account of dozens of types of communities both in the past and the present vegetation of the Americas. It also describes the phases of development step by step, tracking the geologic changes and the shifting vegetation as revealed by pollen and macro fossils. The author is a noted paleobotanist at the Missouri Botanic Garden. There are good photos, maps and graphs of changing temperatures over the epoch. Truly a history of nature.
Graham also has excellent chapters on the techniques of paleoclimate reconstruction and the collection and interpretation of fossils. The text is also a wonderful travelogue, full of historical and prehistorical anecdotes, and covering the modern biogeography of the new world as well as the story of how it came to be as it is.