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Ecology and Evolutionary Biology

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Articles 16141 - 16170 of 19704

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Restoration Of The Red Wolf, Michael K. Phillips, V. Gary Henry, Brian T. Kelly Jan 2003

Restoration Of The Red Wolf, Michael K. Phillips, V. Gary Henry, Brian T. Kelly

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

"WOLFERS" IN NORTHEASTERN North Carolina were busy on February 5, 1768. Records from the Tyrrell County courthouse read:

Giles Long and Thomas Wilkinson awarded one pound for a certified wolf scalp; Jeremiah Norman awarded two pounds for certified wolf and wild-cat scalps; Davenport Smithwick awarded one pound for a certified wolf-scalp.

Such was the nature of the war on the wolf: people killed them for money. The belief of the time held that the war was necessary because it was humankind's manifest destiny to tame the wilderness. And for the wilderness to be tame, the wolf had to be exterminated. …


Wolf-Prey Relations, L. David Mech, Rolf O. Peterson Jan 2003

Wolf-Prey Relations, L. David Mech, Rolf O. Peterson

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

AS 1 (L. o. MECH) watched from a small ski plane while fifteen wolves surrounded a moose on snowy Isle Royale, I had no idea this encounter would typify observations I would make during 40 more years of studying wolf-prey interactions.

My usual routine while observing wolves hunting was to have my pilot keep circling broadly over the scene so I could watch the wolves' attacks without disturbing any of the animals. Only this time there was no attack. The moose held the wolves at bay for about 5 minutes (fig. p), and then the pack left.

From this observation …


Ecological Games In Space And Time: The Distribution And Abundance Of Antarctic Krill And Penguins, Suzanne Alonzo, Paul Switzer, Marc Mangel Jan 2003

Ecological Games In Space And Time: The Distribution And Abundance Of Antarctic Krill And Penguins, Suzanne Alonzo, Paul Switzer, Marc Mangel

Faculty Research & Creative Activity

The distribution and abundance of organisms are affected by behaviors, such as habitat selection, foraging, and reproduction. These behaviors are driven by interactions within and between species, environmental conditions, and the biology of the species in-volved. Although extensive theoretical work has explored predator–prey dynamics, these models have not considered the impact of behavioral plasticity and life-history trade-offs on predicted patterns. We apply a modeling method that allows the consideration of a spatial, dynamic ecological game between predators and prey using a life-history perspec-tive. As an illustrative example, we model the habitat selection of Antarctic krill and penguins during the time …


Utah Forest Health Report : A Baseline Assessment 1999 - 2001, Colleen Keyes, Paul Rogers, Leon Lamadeleine, Vick Applegate, Dave Atkins Jan 2003

Utah Forest Health Report : A Baseline Assessment 1999 - 2001, Colleen Keyes, Paul Rogers, Leon Lamadeleine, Vick Applegate, Dave Atkins

The Bark Beetles, Fuels, and Fire Bibliography

This report addresses forest health in two ways: by discussion of forest-related issues and by data summaries in several appendices. FHM is a long-term monitoring program and therefore, the data presented in this report must be viewed in that light. This report presents a first-time, or baseline summary. Subsequent reports will address changes over time as plots and other detection surveys are conducted and re-measured.


Ecological Games In Space And Time: The Distribution And Abundance Of Antarctic Krill And Penguins, Suzanne H. Alonzo, Paul V. Switzer, Marc Mangel Jan 2003

Ecological Games In Space And Time: The Distribution And Abundance Of Antarctic Krill And Penguins, Suzanne H. Alonzo, Paul V. Switzer, Marc Mangel

Faculty Research & Creative Activity

The distribution and abundance of organisms are affected by behaviors, such as habitat selection, foraging, and reproduction. These behaviors are driven by interactions within and between species, environmental conditions, and the biology of the species in-volved. Although extensive theoretical work has explored predator–prey dynamics, these models have not considered the impact of behavioral plasticity and life-history trade-offs on predicted patterns. We apply a modeling method that allows the consideration of a spatial, dynamic ecological game between predators and prey using a life-history perspec-tive. As an illustrative example, we model the habitat selection of Antarctic krill and penguins during the time …


An Ecosystem-Based Approach To Management: Using Individual Behaviour To Predict The Indirect Effects Of Antarctic Krill Fisheries On Penguin Foraging, Suzanne Alonzo, Paul Switzer, Marc Mangel Jan 2003

An Ecosystem-Based Approach To Management: Using Individual Behaviour To Predict The Indirect Effects Of Antarctic Krill Fisheries On Penguin Foraging, Suzanne Alonzo, Paul Switzer, Marc Mangel

Faculty Research & Creative Activity

Summary 1. Changes in species' abundance and distributions caused by human disturbances can have indirect effects on other species in a community. Although ecosystem approaches to management are becoming increasingly prevalent, they require a fuller understand- ing of how individual behaviour determines interactions within and between species. 2. Ecological interactions involving krill are of major importance to many species within the Antarctic. Despite extensive knowledge of the ecosystem that they occupy, there is still incomplete understanding of the links between species and the effect of environmental conditions on these interactions. In this study, we extended a behavioural model used previously …


Effects Of Experience And Body Size On Refuge Choice In The Crayfish Orconectes Immunis, Patrick Forsythe, Deborah Wyatt, Paul Switzer Jan 2003

Effects Of Experience And Body Size On Refuge Choice In The Crayfish Orconectes Immunis, Patrick Forsythe, Deborah Wyatt, Paul Switzer

Faculty Research & Creative Activity

We investigated whether refuge size or experience with a refuge affected the refuge use of male Orconectes immunis crayfish. Individuals were given choices among seven refuges for 10 consecutive days. Refuges were formed from equal length but different diameter PVC pipe and placed in an array in a random sequence. Three treatments were used. In the Novel Refuge treatment, individuals were placed in a new test arena with a new arrangement of cleaned refuges every day. In the Nonremoval treatment, individuals were left in the same arena with the same set of refuges each day. In the Removal treatment, individuals …


Wild Horses And Burros In The United States, Allen T. Rutberg Jan 2003

Wild Horses And Burros In The United States, Allen T. Rutberg

State of the Animals 2003

Treatment of wild horses and burros has improved remarkably over the last fifty years. In the mid-twentieth century, free-ranging horses and burros suffered horribly at the hands of “mustangers” who captured them at will and whim, sometimes using the most brutal of techniques, including aerial pursuit and shooting or crippling key herd members. The horses were packed into livestock trucks hurt, bleeding, and exhausted, and shipped to slaughter without stopping for rest or watering (Ryden 1999). Unprotected by law, only the good will of a few ranchers protected these abused animals. Public awareness of the plight of the wild horses …


The Science And Sociology Of Hunting: Shifting Practices And Perceptions In The United States And Great Britain, John W. Grandy, Elizabeth Stallman, David W. Macdonald Jan 2003

The Science And Sociology Of Hunting: Shifting Practices And Perceptions In The United States And Great Britain, John W. Grandy, Elizabeth Stallman, David W. Macdonald

State of the Animals 2003

Between the late nineteenth and early twenty-first centuries, both the rationale for and perception of hunting shifted in the United States, coinciding with demographic changes in the U.S. population (Duda 1993). Similar changes in attitude, though largely undocumented, probably occurred in the United Kingdom. (For example, foxhunting did not emerge as a substantial sport until the second half of the eighteenth century; before that, foxes were widely perceived as pests and killed whenever the opportunity arose [Marvin 2000]). Our purpose in this chapter is to compare these two countries in order to reveal some of the science and the sociology …


Nest Building In Captive Gorilla Gorilla Gorilla, Kristen E. Lukas, Tara S. Stoinski, Kyle Burks, Rebecca Snyder, Sarah Bexell, Terry L. Maple Jan 2003

Nest Building In Captive Gorilla Gorilla Gorilla, Kristen E. Lukas, Tara S. Stoinski, Kyle Burks, Rebecca Snyder, Sarah Bexell, Terry L. Maple

Sentience Collection

Although various aspects of gorilla nest building have been described in wild populations, nest-building behavior of captive gorillas has not been subject to much scientific review. We observed nest building in 17 gorillas during three periods: summer baseline, winter baseline, and winter treatment, in which the amount of available nesting material was doubled. We conducted observations exclusively in the indoor holding area in the hour following evening departure of animal care staff. During baseline, gorillas engaged in nest-building on 3.1% of scans and were on a constructed nest on 27.9% of scans. Overall, gorillas spent significantly more time on elevated …


Spatial Heterogeneity Of Soil Nutrients, Nitrogen Dynamics, And Vegetation In A 3rd Order Stream Floodplain In Southwestern West Virginia, David Allen Dick Jan 2003

Spatial Heterogeneity Of Soil Nutrients, Nitrogen Dynamics, And Vegetation In A 3rd Order Stream Floodplain In Southwestern West Virginia, David Allen Dick

Theses, Dissertations and Capstones

Soil processes often exhibit spatial heterogeneity within ecosystems and this heterogeneity may influence community structure. This study was conducted to determine spatial patterns and variability of soil nutrients and plant communities within different vegetation types in a stream floodplain in southwestern West Virginia. One 5-m × 5-m site was established in each of three vegetation/drainage types: pasture (PA), old field (OF), and wetland scar (SC). Pasture and SC sites were located ~25 m apart on flat bottomland; the OF site was located on a moderate slope 6.3 m above bottomland, ~200 m from PA and SC. A 10-m × 1-m …


Growth And The Expression Of Alternative Life Cycles In The Salamander Ambystoma Talpoideum (Caudata: Ambystomatidae), Travis J. Ryan, Raymond D. Semlitsch Jan 2003

Growth And The Expression Of Alternative Life Cycles In The Salamander Ambystoma Talpoideum (Caudata: Ambystomatidae), Travis J. Ryan, Raymond D. Semlitsch

Scholarship and Professional Work - LAS

Complex life cycles (CLCs) contain larval and adult phases that are morphologically and ecologically distinct. Simple life cycles (SLCs) have evolved from CLCs repeatedly in a wide variety of lineages but the processes that may underlie the transition have rarely been identified or investigated experimentally. We examined the influence of larval growth rate on the facultative expression of alternative life cycles (metamorphosis or maturation as gill-bearing adults [= paedomorphosis]) in the salamander Ambystoma talpoideum. We manipulated growth rates by altering the amount of food individuals received throughout larval development. The expression of alternative life cycles in A. talpoideum is influenced …


Fishes Of The Red River In Arkansas, Thomas M. Buchanan, Drew Wilson, L. G. Claybrook, William G. Layher Jan 2003

Fishes Of The Red River In Arkansas, Thomas M. Buchanan, Drew Wilson, L. G. Claybrook, William G. Layher

Journal of the Arkansas Academy of Science

Fishes were collected from Red River mainstem habitats in Arkansas with seines, rotenone, hoop nets, gill nets, and trotlines from 1995 through 2001. Seventy-two species were identified distributed among 17 families, and 15 species were new records for the Red River in Arkansas. Eighty-three species are now historically known from the Arkansas segment of the Red River. Approximately 67% of the fishes known from the entire Red River have been found in the Arkansas segment, which is only 11% of the entire river length. Baseline data on the fish fauna of the Red River is critical for the analysis of …


Subterranean Biodiversity Of Arkansas, Part 1: Bioinventory And Bioassessment Of Caves In The Sylamore Ranger District, Ozark National Forest, Arkansas, G. O. Graening, Michael E. Slay, Karen K. Tinkle Jan 2003

Subterranean Biodiversity Of Arkansas, Part 1: Bioinventory And Bioassessment Of Caves In The Sylamore Ranger District, Ozark National Forest, Arkansas, G. O. Graening, Michael E. Slay, Karen K. Tinkle

Journal of the Arkansas Academy of Science

Inventory and assessment of subterranean ecosystems of the Sylamore Ranger District (within Baxter, Marion, Searcy, and Stone counties) Ozark National Forest, was performed 2000 to 2002. The Sylamore District, completely underlaid in karst topography (occurring in Mississippian to Ordovician carbonates), contains approximately 10% of the known caves in Arkansas. Thirty-five sites were inventoried, six of which were sampled for environmental quality. These were combined and analyzed with previous studies, creating a database of 1,238 total species occurrences, 230 species, and 61 total sites. Most common were cave crickets, pipistrelle bats, woodrats, mosquitoes, and spiders. Fourteen species obligate to coves or …


Acoustic Mapping Of Aquatic Vegetation In Lakes: An Example From Northwest Arkansas, Angela M. Polly, Stephen K. Boss Jan 2003

Acoustic Mapping Of Aquatic Vegetation In Lakes: An Example From Northwest Arkansas, Angela M. Polly, Stephen K. Boss

Journal of the Arkansas Academy of Science

No abstract provided.


Investigation Of Matrilineal Relationships Via Mitochondrial Dna In The Southeastern Yellowjacket (Vespula Squamosa), Anthony Deets Jan 2003

Investigation Of Matrilineal Relationships Via Mitochondrial Dna In The Southeastern Yellowjacket (Vespula Squamosa), Anthony Deets

Masters Theses

The question of whether and how apparently "altruistic" behaviors can evolve in social animals has received an enormous amount of attention from evolutionary biologists and has been termed "the central theoretical problem of sociobiology". Thus, recent interest is eusocial species with coexisting multiple queens stems from the realization that the genetic relatedness of individuals in such colonies presents additional theoretical challenges beyond those addressed by the Hamiltonian model of kin selection and lengthens the potential list of reproductive conflicts of interest.

The Southeastern Yellowjacket (Vespula squamosa) exhibits two social forms sympatrically in the southern parts of its range. These two …


The Effect Of Aposematic Coloration On The Food Preference Of Aphelocoma Coerulescens, The Florida Scrub Jay, Mary Elizabeth Hill Jan 2003

The Effect Of Aposematic Coloration On The Food Preference Of Aphelocoma Coerulescens, The Florida Scrub Jay, Mary Elizabeth Hill

Theses and Dissertations

Aposematic coloration, commonly observed in noxious organisms, serves as a warning to predators to avoid attacking specific prey. This coloration is conspicuous in nature, with one of the most common examples being a red and black pattern. The plant Abrus precatorius exhibits this warning signal in its seeds, which resemble lady beetles and contain the concentrated toxin abrin. Aphelocoma coerulescens, an endemic and federally threatened bird in the state of Florida, shares a similar distribution with Abrus precatorius, making interaction between the two species possible. Using an edible model of the Abrus seed, this potential interaction was tested in Martin …


Demographic Assessment Of The Blue Crab (Callinectes Sapidus) In Chesapeake Bay Using Extractable Lipofuscins As Age Markers, Se-Jong Ju, David H. Secor, H. Rodger Harvey Jan 2003

Demographic Assessment Of The Blue Crab (Callinectes Sapidus) In Chesapeake Bay Using Extractable Lipofuscins As Age Markers, Se-Jong Ju, David H. Secor, H. Rodger Harvey

OES Faculty Publications

The blue crab (Callinectes sapidus) plays an important economic and ecological role in estuaries and coastal habitats from the Gulf of Mexico to the east coast of North America, but demographic assessments are limited by length-based methods. We applied an alternative aging method using biochemical measures of metabolic byproducts (lipofuscins) sequestered in the neural tissue of eyestalks to examine population age structure. From Chesapeake Bay, subsamples of animals collected from the 1998-99 (n-769) and 1999-2000 (n=367) winter dredge surveys were collected and lipofuscin was measured. Modal analysis of the lipofuscin index provided separation into three modes, whereas carapace-width …


Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert Jan 2003

Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert

OES Faculty Publications

Amino acid oxidation (AAO) and peptide hydrolysis (PH) are processes affecting the recycling of organic material and nutrients. We compared extracellular AAO and PH rates to C and N uptake rates along estuarine gradients of salinity, nutrients and productivity in the Pocomoke River, a subestuary of the Chesapeake Bay. This estuary is seasonally depleted in inorganic N, and rich in dissolved organic material (DOM) throughout the year. AAO, PH, and N uptake rates measured in 1999 and 2000 were not limited to particular size fractions measured, or to auto- or heterotrophic groups of organisms. At a station near the turbidity …


Nest-Site Selection In The Eastern Box Turtle, Terrapene Carolina Carolina, In A Population In Central Illinois, Beth Flitz Jan 2003

Nest-Site Selection In The Eastern Box Turtle, Terrapene Carolina Carolina, In A Population In Central Illinois, Beth Flitz

Masters Theses

Nest site selection in turtles might allow females to increase the survival of their offspring but little is known about the variables that influence that choice. I examined the microhabitat variables at nest sites of the eastern box turtle, Terrapene carolina carolina, at a Boy Scout camp in Shelby County, Illinois, to determine if females chose nest sites that differed from random sites within the camp. Nest sites differed from random sites in vegetation height and composition, percentage ground and canopy cover, and light intensity. All females placed their nests in open habitat within the camp or a pasture bordering …


The Recovery Of Birds Through Farmland Revegetation In The Shire Of Goomalling, Western Australia, Rebecca Heath Jan 2003

The Recovery Of Birds Through Farmland Revegetation In The Shire Of Goomalling, Western Australia, Rebecca Heath

Theses : Honours

The birds of grazed paddocks, early revegetation (less than three years in age), three to seven year old revegetation, older revegetation (greater than seven years in age) and remnant vegetation were surveyed over the course of one year to determine whether revegetation recovers avian biodiversity in agricultural landscapes. Habitat features that were useful to the birds, and those that were missing from revegetation, were identified in order to broaden the knowledge base of faunal use of farmland revegetation, and aid in the devising of successful revegetation strategies. Notable differences in the abundance and composition of birds were found between the …


Good Intentions May Doom Aspen Groves, James R. Fazio Jan 2003

Good Intentions May Doom Aspen Groves, James R. Fazio

Aspen Bibliography

If there were a Guiness Book of World Records for trees, quaking aspen would be in it - not once but probably several times.


Winter 2003, Nsu Oceanographic Center Jan 2003

Winter 2003, Nsu Oceanographic Center

Currents

No abstract provided.


Review Of The Nature Of Nebraska: Ecology And Biodiversity Paul A. Johnsgard, L. Lareesa Wolfenbarger Jan 2003

Review Of The Nature Of Nebraska: Ecology And Biodiversity Paul A. Johnsgard, L. Lareesa Wolfenbarger

Biology Faculty Publications

As a newcomer to Nebraska and someone learning the natural history of this place, I thoroughly enjoyed The Nature of Nebraska. More consequentially, the book will serve as a valuable resource for longtime naturalists, teachers, and others who want to learn about Nebraska's natural history.

Opening with a discussion of geology and ecology, Johnsgard offers a broad overview of Nebraska's ecological diversity, intertwining material on the natural forces that have historically dominated the Plains with a discussion of the anthropogenic forces currently altering the region's unique ecological nature. Approximately half of the book is devoted to more specific descriptions …


Wolves And Humans, Steven H. Fritts, Robert O. Stephenson, Robert D. Hayes, Luigi Boitani Jan 2003

Wolves And Humans, Steven H. Fritts, Robert O. Stephenson, Robert D. Hayes, Luigi Boitani

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

TRY TO IMAGINE a small group of wolves sitting at a table engaged in vigorous debate. These wolves are from various parts of the globe and are perhaps a bit more scholarly than most. In fact, they are especially knowledgeable about the biology of that notorious two-legged species, Homo sapiens. They have been brought together to document their relationship with humans over the last several millennia. Pause for a few moments and consider what they might say ...

Perhaps the wolves' discussion would chronicle the evils of the human species, including details of atrocities committed against lupine ancestors down …


Wolves: Behavior, Ecology, And Conservation: Photo Section I, Douglas W. Smith, Rolf Peterson, L. David Mech, Barron Crawford Jan 2003

Wolves: Behavior, Ecology, And Conservation: Photo Section I, Douglas W. Smith, Rolf Peterson, L. David Mech, Barron Crawford

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

Wolves in Yellowstone National Park's restored population often must compete with grizzly bears at the carcasses of their kills. Especially after their first feeding at a kill, wolves tend to relinquish their kills to bears. Photograph by Doug Smith.

Elk are one of the most common prey of wolves in the northern Rocky Mountains of North America, primarily because in most areas they tend to outnumber other prey. This large bull standing his ground escaped this pack. Photograph by Doug Smith.


Survival Of The Western Pond Turtle (Emys Marmorata) In An Urban California Environment, Phillip Q. Spinks, Gregory B. Pauly, John J. Crayon, H. Bradley Shaffer Jan 2003

Survival Of The Western Pond Turtle (Emys Marmorata) In An Urban California Environment, Phillip Q. Spinks, Gregory B. Pauly, John J. Crayon, H. Bradley Shaffer

United States Geological Survey: Staff Publications

The western pond turtle Emys (formerly Clemmys marmorata) is declining throughout its range, primarily due to loss of habitat via urbanization and conversion to agriculture. Urban waterways present several important challenges to freshwater turtle populations, but they also present an opportunity to maintain declining species in a ubiquitous habitat that has high public visibility. The arboretum waterway on the University of California, Davis campus is an example of an extensively altered urban habitat that supports a relatively large E. marmorata population. Over the last 6 years, we monitored the turtle population inhabiting the arboretum waterway to determine the …


Expression Of Susceptibility To Fusarium Head Blight And Grain Mold In A1 And A2 Cytoplasms Of Sorghum Bicolor, James P. Stack, Jeffrey F. Pedersen Jan 2003

Expression Of Susceptibility To Fusarium Head Blight And Grain Mold In A1 And A2 Cytoplasms Of Sorghum Bicolor, James P. Stack, Jeffrey F. Pedersen

West Central Research and Extension Center, North Platte

Panicle diseases are among the major constraints to sorghum (Sorghum bicolor) production in the northern Great Plains; host plant resistance is the primary management option. However, essentially all commercial sorghum hybrids contain A1 cytoplasm, which raises the concern about increased disease risk as a result of cytoplasmic genetic uniformity. To determine the influence of cytoplasmic background on the expression of susceptibility to panicle diseases, F1 hybrids with four nuclear genotypes in each of two cytoplasms (A1 and A2) were planted in three environmentally diverse geographic locations in Nebraska. Fusarium head blight ranged in …


Infant Mortality After Takeovers In Wild Ethiopian Hamadryas Baboons, Larissa Swedell, Teklu Tesfaye Jan 2003

Infant Mortality After Takeovers In Wild Ethiopian Hamadryas Baboons, Larissa Swedell, Teklu Tesfaye

Publications and Research

In this paper, we report the first observational evidence of infanticide in wild hamadryas baboons. The study group inhabits the lowlands of the northern Rift Valley in Ethiopia and has been under observation for over 1200 hours, on and off, since October 1996. Here we report observations from August and September 2002 of the consequences of two takeovers of known females with black infants. After the first takeover, the respective infant disappeared and was presumed dead within eleven days of the takeover. After the second takeover, the infant incurred repeated severe aggression from its mother’s new leader male and eventually …


Human Health Effects Of A Changing Global Nitrogen Cycle, Alan R. Townsend, Robert W. Howarth, Fakhri A. Bazzaz, Mary S. Booth, Cory C. Cleveland, Sharon K. Collinge, Andrew P. Dobson, Paul R. Epstein, Elisabeth A. Holland, Dennis R. Keeney, Michael A. Mallin, Christine A. Rogers, Peter Wayne, Amir H. Wolfe Jan 2003

Human Health Effects Of A Changing Global Nitrogen Cycle, Alan R. Townsend, Robert W. Howarth, Fakhri A. Bazzaz, Mary S. Booth, Cory C. Cleveland, Sharon K. Collinge, Andrew P. Dobson, Paul R. Epstein, Elisabeth A. Holland, Dennis R. Keeney, Michael A. Mallin, Christine A. Rogers, Peter Wayne, Amir H. Wolfe

Ecosystem and Conservation Sciences Faculty Publications

Changes to the global nitrogen cycle affect human health well beyond the associated benefits of increased food production. Many intensively fertilized crops become animal feed, helping to create disparities in world food distribution and leading to unbalanced diets, even in wealthy nations. Excessive air- and water-borne nitrogen are linked to respiratory ailments, cardiac disease, and several cancers. Ecological feedbacks to excess nitrogen can inhibit crop growth, increase allergenic pollen production, and potentially affect the dynamics of several vector-borne diseases, including West Nile virus, malaria, and cholera. These and other examples suggest that our increasing production and use of fixed nitrogen …