Vascular plant extinction in the continental United States and Canada

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.     

Variation among congeneric dinoflagellates from the northeastern United States and Canada

Relationships among dinoflagellates of the genus Alexandrium (=Protogonyaulax) from Long Island, New England, USA, and northeastern Canada were investigated between 1983 and 1987 using enzyme electrophoresis. A relative lack of heterogeneity among toxic isolates was observed despite large geographic separations of source populations. This observation is in marked contrast to observations on toxic members of this genus from the west coast of Canada and the United States. These different enzyme variability patterns support the proposal that dispersal of toxic strains in the east from a common source has occurred recently, presumably from established populations in northern Maine, USA, or Canada. Non-toxic strains from the study area were only distantly related to toxic isolates, consistent with their different morphology and separate species designations. One non-toxic isolate from a different region, that is conspecific with a number of the toxic strains, was more similar to these isolates than to other non-toxic clones.     

Biogeography of toxic dinoflagellates in the genusAlexandrium from the northeastern United States and Canada

Twenty-eight strains of toxic dinoflagellates in the genusAlexandrium from the northeastern United States and Canada were characterized on the basis of morphology, bioluminescence capacity, mating compatibility, and toxin composition. The distributions of these characters were evaluated in the context of regional patterns of paralytic shellfish poisoning (PSP) and coastal hydrography. Two morphospecies were identified-A. tamarense Lebour andA. fundyense Balech. The two are interspersed geographically though there are areas, such as the Gulf of Maine, where apparently onlyA. fundyense occurs. Southern waters (Cape Cod, Connecticut, and Long Island) have especially diverse populations. The two species are sexually compatible. Virtually all northern isolates are bioluminescent, whereas southern isolates include bioluminescent and non-bioluminescent strains. Cluster analyses, based on high performance liquid chromatography (HPLC) determinations of the suite of toxins produced by each isolate, revealed two and perhaps three distinct groups. One is comprised almost exclusively of northern strains, and the other of southern strains. A Cape Cod cluster may be separable from the southern group. These analyses explain a previously reported north-to-south trend of decreasing toxicity, as the northern isolates produce greater proportions of the more potent toxins than do southern forms. The overall perspective is that the biogeography of toxicAlexandrium spp. in the study region is not that of a single, widespread, homogeneous population, but rather is comprised of several sub-populations, each with its own physiological characteristics and history. Two scenarios are considered with respect to this regional biogeography. The first invokes recent and continuing dispersal of isolates to the south from a center of origin in the north, followed by recombination and strong selection. The second holds that the northern and southern populations diverged from a common ancestor (vicariance), but now represent localized populations with little mixing of genotypes. Neither hypothesis can be completely refuted by the data presented here, though the weight of the evidence favors the latter. The correct scenario may be a combination of both, with recent and continuous speading occuring within the Gulf of Maine and perphaps the Gulf of St. Laerence, but with endemic localized populations persisting without genetic exchange in most southern locations. These data also indicate that although morphological criteria separate toxicAlexandrim isolates from the study region into two morphospecies, these assignments do not coincide with clusterings based on toxin composition or allozyme electrophoresis, and they are further violated by mating results. A revision of taxon designations to the varietal level could be justified.     

The United States Environmental Protection Agency's Role in Controlling Aquatic Debris

Unsightly and environmentally damaging debris is an ever present problem for waterways and beaches around the world. This debris has numerous sources, and is comprised of materials ranging from metal and wood to plastics and paper. the aesthetic, economic, and environmental impacts of debris have been well documented over the past several years. in an effort to control the release of trash and debris into our waters, there are many activities ongoing in the US. One such activity is a coordinated effort between the US Environmental Protection Agency (EPA), other federal Agencies (National Oceanic and Atmospheric Administration (NOAA), United States Coast Guard (USCG), United States Navy (USN), National Park Service (NPS), Department of Interior (DOI)), industry (the Society of the Plastics Industry, INC. (SPI)), environmental, and local groups. This paper describes the results of field assessments, and the other activities undertaken by EPA as part of this coordinated effort to control the release of debris to our nation's waterways.     

The United States Environmental Protection Agency's Role in Controlling Aquatic Debris

Unsightly and environmentally damaging debris is an ever present problem for waterways and beaches around the world. This debris has numerous sources, and is comprised of materials ranging from metal and wood to plastics and paper. the aesthetic, economic, and environmental impacts of debris have been well documented over the past several years. in an effort to control the release of trash and debris into our waters, there are many activities ongoing in the US. One such activity is a coordinated effort between the US Environmental Protection Agency (EPA), other federal Agencies (National Oceanic and Atmospheric Administration (NOAA), United States Coast Guard (USCG), United States Navy (USN), National Park Service (NPS), Department of Interior (DOI)), industry (the Society of the Plastics Industry, INC. (SPI)), environmental, and local groups. This paper describes the results of field assessments, and the other activities undertaken by EPA as part of this coordinated effort to control the release of debris to our nation's waterways.     

The Botanist Effect Revisited: Plant Species Richness, County Area, and Human Population Size in the United States

Abstract:  The "botanist effect" is thought to be the reason for higher plant species richness in areas where botanists are disproportionately present as an artefactual consequence of a more thorough sampling. We examined whether this was the case for U.S. counties. We collated the number of species of vascular plants, human population size, and the area of U.S. counties. Controlling for spatial autocorrelation and county area, plant species richness increased with human population size and density in counties with and without universities and/or botanical gardens, with no significant differences in the relation between the two subsets. This is consistent with previous findings and further evidence of a broad-scale positive correlation between species richness and human population presence, which has important consequences for the experience of nature by inhabitants of densely populated regions. Combined with the many reports of a negative correlation between the two variables at a local scale, the positive relation between plant species richness in U.S. counties and human population presence stresses the need for the conservation of seminatural areas in urbanized ecosystems and for the containment of urban and suburban sprawl.     

Simulated Responses of a Forest-Interior Bird Population to Forest Management Options in Central Hardwood Forests of the United States

I used estimates of carrying capacity, survival, fecundity, and edge effects to simulate the responses of a forest-interior bird population to selection cutting clearcutting, and no timber harvest. I also modeled population sensitivity to changes in fecundity, survival, K , and edge relationships. Because model parameters are based on scant data, results should he regarded as hypotheses to be further investigated or measures of the relative impact or sensitivity (given model assumptions). Simulated population size was greater with no timber harvest than with clearcutting and greater with clearcutting than with group selection when edge effects were included in the model. Without edge effects, population levels were only slightly lower under group selection than under no timber harvest, and greater than clearcutting. Edge effects had only a small impact on population levels under clearcutting. Clearcut size did not have much effect on population levels, but longer and shorter rotation ages resulted in higher and lower population levels, respectively. The model was very sensitive to declines in mean fecundity and survival, suggesting that factors affecting mean demographic rates could be more important than local edge effects. Some methods of timber harvest may be compatible with the conservation of forest-interior birds, but better demographic data and information on habitat suitability of selectively cut forests and young even-aged stands is needed to adequately evaluate management options.     

Conservation Deficits for the Continental United States: an Ecosystem Gap Analysis

Abstract:  Few attempts have been made to analyze the status of conservation efforts at a continental scale, mainly because of the lack of high-quality data sets at this scale. Given that land management agencies want to prioritize conservation efforts and spend limited resources wisely, we recognized the need to undertake a national gap analysis. We developed the most detailed national vegetation cover map feasible to analyze the degree of representation of ecosystem analysis units (an initial representation of ecosystem types) in the network of conservation lands for the continental United States. We combined The Nature Conservancy's ecoregions with the natural land-cover types of the National Land Cover Data Set and examined the conservation status of each combination. The majority of ecosystem analysis units have a small percentage of their total area residing in lands that are managed to support biodiversity. The median percentage of area conserved on status 1 and 2 lands (highest of four levels of protection) as designated by the Gap Analysis Program for the 554 ecosystem analysis units is 4.0% (SD 18.1%). This finding, which highlights our national conservation deficits, points to the need to address the size and diversity of the conservation estate.     

Old-Growth Mangrove Forests in the United States

Criteria used to identify old-growth forests in the Pacific Northwest have not been proven applicable in other ecological life zones. For example, Pacific Northwest criteria are not suitable for the identification of old-growth mangrove forests. To identify old-growth mangroves one has to take into account differences in stand structure and function due to geomorphology, within-site environmental gradients, and regional disturbance regimes. A flexible and holistic approach is needed. Stand age, defined in terms of Pacific Northwest forests, is not necessarily the best criterion for identifying for conservation mangrove forests or any forest outside the Pacific Northwest. No single stand will have all old-growth characteristics, and even if they are present in a stand, these characteristics do not necessarily assure that the stand is old growth. Whether a mangrove stand reaches old-growth stage depends on the dynamics of coastal conditions under which it grows. Moreover, it is necessary to differentiate between the age of trees in a stand and the age of the mangrove system, which includes the substrate. Old-growth mangrove stands are improbable states for this ecosystem type, and they can revert to younger stages. Mangroves offer a challenge to the concept of the old-growth forest, and through our analysis of this system we show that when ecosystem functions and states are evaluated it is necessary to avoid geographic biases based on particular ecological conditions.     

Status of Marine Mammals in the United States

Abstract: The 1994 amendments to the U.S. Marine Mammal Protection Act required, for the first time, an assessment of the status of every marine mammal stock in the United States. We draw conclusions about the status of marine mammals from assessments of 153 stocks conducted to meet the requirements of these amendments. We found important regional differences in the status of stocks. Most stocks in the Atlantic and Pacific experience human-induced mortality (takes), primarily from gill-net fisheries. The proportion of stocks with takes was lower in the Gulf of Mexico and Hawaii, areas with few gill-net fisheries. Estimated takes exceeded removal limits for 29% of stocks in the Atlantic, 14% in the Pacific, 8% in Alaska, 7% in the Gulf of Mexico, and 0% in Hawaii. Twenty-eight stocks are listed as threatened or endangered under the U.S. Endangered Species Act. Most, but not all, baleen whale stocks are recovering after cessation of commercial harvests. Many species of pelagic cetaceans, including beaked and sperm whales, are vulnerable to mortality in pelagic drift-net fisheries. Most pinniped stocks experience takes, but none of these takes exceeds removal limits, and all pinniped stocks on mainland coasts of the United States are increasing in abundance. Quantitative data on trends in abundance are available for few cetacean stocks, emphasizing the difficulty of monitoring trends in these species. These stock assessments have greatly advanced our understanding of the status of marine mammals in the United States, but information gaps remain, particularly regarding stock structure and possible mortality in unmonitored fisheries.     

Modeled historical land use and land cover for the conterminous United States

The landscape of the conterminous United States has changed dramatically over the last 200 years, with agricultural land use, urban expansion, forestry, and other anthropogenic activities altering land cover across vast swaths of the country. While land use and land cover (LULC) models have been developed to model potential future LULC change, few efforts have focused on recreating historical landscapes. Researchers at the US Geological Survey have used a wide range of historical data sources and a spatially explicit modeling framework to model spatially explicit historical LULC change in the conterminous United States from 1992 back to 1938. Annual LULC maps were produced at 250-m resolution, with 14 LULC classes. Assessment of model results showed good agreement with trends and spatial patterns in historical data sources such as the Census of Agriculture and historical housing density data, although comparison with historical data is complicated by definitional and methodological differences. The completion of this dataset allows researchers to assess historical LULC impacts on a range of ecological processes.