This statistic shows the change in the regional distribution of the U.S. population each decade from 1790 to 2021. In 2021, 17.2 percent of the population in the United States lived in the Northeast.

In 2023, Washington, D.C. had the highest population density in the United States, with 11,130.69 people per square mile. As a whole, there were about 94.83 residents per square mile in the U.S., and Alaska was the state with the lowest population density, with 1.29 residents per square mile. The problem of population density Simply put, population density is the population of a country divided by the area of the country. While this can be an interesting measure of how many people live in a country and how large the country is, it does not account for the degree of urbanization, or the share of people who live in urban centers. For example, Russia is the largest country in the world and has a comparatively low population, so its population density is very low. However, much of the country is uninhabited, so cities in Russia are much more densely populated than the rest of the country. Urbanization in the United States While the United States is not very densely populated compared to other countries, its population density has increased significantly over the past few decades. The degree of urbanization has also increased, and well over half of the population lives in urban centers.

These files contain the spatial boundaries of the NOAA Fisheries Bottom-trawl surveys. This data set covers 8 regions of the United States: Northeast, Southeast, Gulf of Mexico, West Coast, Bering Sea, Aleutian Islands, Gulf of Alaska, and Hawai'i Islands.

Since the turn of the century, the United States has undergone a redistribution of population from rural and rust belt counties to urban counties; particularly those along the Northern and Southern Atlantic Seaboard, the Pacific Coast and parts of the Southwest region. 41 percent or 1,295 counties had population declines from 2000 to 2016, with 15 counties experiencing declines of more than 25,000 people or 2.4 percent of the total population.Over the same period, total population for the nation grew by 42 million, 8 percent of which has migrated from declining rural and rust belt counties to growing urban counties along the East and West Coast, and in the Southwest, resulting in a 23 percent increase in population occurring in 60 percent of counties in the United States. The data indicates that the majority of this growth is occurring in just 12 percent of counties, including the San Francisco Bay Region which has experienced a 2.4 percent increase in population.

These files contain the spatial boundaries of the NOAA Fisheries Bottom-trawl surveys. This data set covers 8 regions of the United States: Northeast, Southeast, Gulf of Mexico, West Coast, Eastern Bering Sea, Aleutian Islands, Gulf of Alaska, and Hawai'i Islands.

The Cetacean Density and Distribution Mapping Working Group identified Biologically Important Areas (BIAs) for 24 cetacean species, stocks, or populations in seven regions (US East Coast, Gulf of Mexico, West Coast, Hawaiian Islands, Gulf of Alaska, Aleutian Islands and Bering Sea, and Arctic [encompassing the northeastern Chukchi and western Beaufort seas]) within US waters. BIAs are reproductive areas, feeding areas, migratory corridors, and areas in which small and resident populations are concentrated. BIAs are region-, species-, and time-specific. Information provided for each BIA includes the following: 1) a written narrative describing the information, assumptions, and logic used to delineate the BIA; 2) a map of the BIA; 3) a list of references used in the assessment; and 4) a metadata table that concisely details the type and quantity of information used to define a BIA, providing transparency in how BIAs were designated in a quick reference table format. BIAs were identified through an expert elicitation process. The delineation of BIAs does not have direct or immediate regulatory consequences. Rather, the BIA assessment is intended to provide the best available science to help inform regulatory and management decisions under existing authorities about some, though not all, important cetacean areas in order to minimize the impacts of anthropogenic activities on cetaceans and to achieve conservation and protection goals. In addition, the BIAs and associated information may be used to identify information gaps and prioritize future research and modeling efforts to better understand cetaceans, their habitat, and ecosystems.

NOAA Fisheries and its partners conduct fisheries-independent surveys in 8 regions in the US (Northeast, Southeast, Gulf of Mexico, West Coast, Gulf of Alaska, Bering Sea, Aleutian Islands, Hawai’i Islands). These surveys are designed to collect information on the seasonal distribution, relative abundance, and biodiversity of fish and invertebrate species found in U.S. waters. Over 900 species of fish and invertebrates have been identified in these surveys.

Aerial surveys are conducted along the US west coast to determine distribution and abundance of endangered leatherback turtles (Dermochelys coriacea), loggerhead turtles (Caretta caretta), and harbor porpoises (Phocoena phocoena). Surveys are conducted in waters between US/Mexico and US/Canada maritime borders, west to the 2000m isobath for leatherbacks, up to 122.8W for loggerheads, and in nearshore waters (approx 200m isobath) between central California and southern Oregon for harbor porpoise.

This region includes the Pacific leatherback conservation area (Federal Register notice 77 (17) FR 4170, January 26, 2012). Previous knowledge of leatherback turtle use of US EEZ waters in the Pacific Northwest came primarily from opportunistic sightings from platforms of opportunity, telemetry deployments that originated from western Pacific nesting beaches (Benson et al. 2007a; 2011), and a previous systematic survey conducted during 2010.

This region also includes a time-area closure off southern California that is to be triggered by warm water anomalies (50 CFR 660.713(c)(2)). This regulation was developed as result of a reasonable and prudent alternative following a formal consultation process as required by Section 7 of the ESA. NMFS developed the rule using information from the fishery observer program for the California drift gillnet fishery, in which all entanglements of loggerhead turtles occurred within a particular sea surface temperature range (15.6 to 22.2 °C). On July 25, 2014, NMFS published notification of an in-season closure for the DGN fishery through the end of August to protect loggerheads in the southern California Bight (79 FR 43268). Based on late spring/early summer forecasts by the Climate Prediction Center, which included an “El Niño watch,” NMFS determined that oceanographic conditions, including anomalously warm sea surface temperatures, warranted the closure. This was the first-ever implementation of this time-area closure, and has resulted in significant attention from commercial fishers, environmental groups, and state and federal agencies regarding the importance southern Californian waters for endangered loggerhead turtles. Little information is available on population abundance and spatial distribution of loggerhead turtles off southern California and how they may change during warm water periods. However, reports of loggerhead turtle sightings from divers and recreational fishers have increased in recent years and the rate of loggerhead strandings along the U.S. west coast is at an all-time high, indicating a regular presence of loggerheads off the coast (NMFS Turtle Stranding Database). Additionally, the Assistant Administrator for NMFS Protected Resources at the West Coast Regional Office has determined that a thorough re-examination of loggerhead time-area closure is a top priority; therefore, this survey is important and timely, given the current anomalously warm water temperatures off southern California.

These files contain the key distribution metrics of center of gravity, range limits, and depth for each species in the portal. This data set covers 7 regions of the United States: Northeast, Southeast, Gulf of Mexico, West Coast, Eastern Bering Sea, Aleutian Islands, and Gulf of Alaska.

Effective management of threatened and exploited species requires an understanding of both the genetic connectivity among populations and local adaptation. The Olympia oyster (Ostrea lurida), patchily distributed from Baja California to the central coast of Canada, has a long history of population declines due to anthropogenic stressors. For such coastal marine species, population structure could follow a continuous isolation-by-distance model, contain regional blocks of genetic similarity separated by barriers to gene flow, or be consistent with a null model of no population structure. To distinguish between these hypotheses in O. lurida, 13,424 single-nucleotide polymorphisms (SNPs) were used to characterize rangewide population structure, genetic connectivity, and adaptive divergence. Samples were collected across the species range on the west coast of North America, from southern California to Vancouver Island. A conservative approach for detecting putative loci under selection identified 235 SNPs across 129 GBS loci, which were functionally annotated and analyzed separately from the remaining neutral loci. While strong population structure was observed on a regional scale in both neutral and outlier markers, neutral markers had greater power to detect fine-scale structure. Geographic regions of reduced gene flow aligned with known marine biogeographic barriers, such as Cape Mendocino, Monterey Bay, and the currents around Cape Flattery. The outlier loci identified as under putative selection included genes involved in developmental regulation, sensory information processing, energy metabolism, immune response, and muscle contraction. These loci are excellent candidates for future research and may provide targets for genetic monitoring programs. Beyond specific applications for restoration and management of the Olympia oyster, this study lends to the growing body of evidence for both population structure and adaptive differentiation across a range of marine species exhibiting the potential for panmixia. Computational notebooks are available to facilitate reproducibility and future open-sourced research on the population structure of Ostrea lurida.

NOAA Fisheries and its partners conduct fisheries-independent surveys in 8 regions in the US (Northeast, Southeast, Gulf of Mexico, West Coast, Gulf of Alaska, Bering Sea, Aleutian Islands, Hawai’i Islands). These surveys are designed to collect information on the seasonal distribution, relative abundance, and biodiversity of fish and invertebrate species found in U.S. waters. Over 900 species of fish and invertebrates have been identified in these surveys.

NOAA Fisheries and its partners conduct fisheries-independent surveys in 8 regions in the US (Northeast, Southeast, Gulf of Mexico, West Coast, Gulf of Alaska, Bering Sea, Aleutian Islands, Hawai’i Islands). These surveys are designed to collect information on the seasonal distribution, relative abundance, and biodiversity of fish and invertebrate species found in U.S. waters. Over 900 species of fish and invertebrates have been identified in these surveys.

NOAA Fisheries and its partners conduct fisheries-independent surveys in 8 regions in the US (Northeast, Southeast, Gulf of Mexico, West Coast, Gulf of Alaska, Bering Sea, Aleutian Islands, Hawai’i Islands). These surveys are designed to collect information on the seasonal distribution, relative abundance, and biodiversity of fish and invertebrate species found in U.S. waters. Over 9...

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead (Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook (O. tshawytscha) in the California Central Valley, coho (O. kisutch) in California and southern Oregon, sockeye (O. nerka) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids.

After a dramatic population decline, Steller sea lions have begun to recover throughout most of their range. However, Steller sea lions in the Western Aleutians and Commander Islands are continuing to decline. Comparing survival rates between regions with different population trends may provide insights into the factors driving the dynamics, but published data on vital rates have been extremely scarce, especially in regions where the populations are still declining. Fortunately, an unprecedented dataset of marked Steller sea lions at rookeries in the Russian Far East is available, allowing us to determine age and sex specific survival in sea lions up to 22 years old. We focused on survival rates in three areas in the Russian range with differing population trends: the Commander Islands (Medny Island rookery), Eastern Kamchatka (Kozlov Cape rookery) and the Kuril Islands (four rookeries). Survival rates differed between these three regions, though not necessarily as predicted by population trends. Pup survival was higher where the populations were declining (Medny Island) or not recovering (Kozlov Cape) than in all Kuril Island rookeries. The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there. However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends. High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas. Resight history of Steller sea lions in the Russian Far EastData file contains annual resight history of Steller sea lions branded as pups between 1989 and 2008 and resighted between 1996 and 2011 at 6 major rookeries in the Russian Far East. Detailed information on data structure provided in read me file.data.csv

Regional scale habitat suitability models provide finer scale resolution and more focused predictions of where organisms may occur. Previous modelling approaches have focused primarily on local and/or global scales, while regional scale models have been relatively few. In this study, regional scale predictive habitat models are presented for deep-sea corals for the U.S. West Coast (California, Oregon and Washington). Model results are intended to aid in future research or mapping efforts and to assess potential coral habitat suitability both within and outside existing bottom trawl closures (i.e. Essential Fish Habitat (EFH)) and identify suitable habitat within U.S. National Marine Sanctuaries (NMS). Deep-sea coral habitat suitability was modelled at 500 m×500 m spatial resolution using a range of physical, chemical and environmental variables known or thought to influence the distribution of deep-sea corals. Using a spatial partitioning cross-validation approach, maximum entropy models identified slope, temperature, salinity and depth as important predictors for most deep-sea coral taxa. Large areas of highly suitable deep-sea coral habitat were predicted both within and outside of existing bottom trawl closures and NMS boundaries. Predicted habitat suitability over regional scales are not currently able to identify coral areas with pin point accuracy and probably overpredict actual coral distribution due to model limitations and unincorporated variables (i.e. data on distribution of hard substrate) that are known to limit their distribution. Predicted habitat results should be used in conjunction with multibeam bathymetry, geological mapping and other tools to guide future research efforts to areas with the highest probability of harboring deep-sea corals. Field validation of predicted habitat is needed to quantify model accuracy, particularly in areas that have not been sampled.

Patterns of population structure and historical genetic demography of blacknose sharks in the western North Atlantic Ocean were assessed using variation in nuclear-encoded microsatellites and sequences of mitochondrial (mt)DNA. Significant heterogeneity and/or inferred barriers to gene flow, based on microsatellites and/or mtDNA, revealed the occurrence of five genetic populations localized to five geographic regions: the southeastern U.S Atlantic coast, the eastern Gulf of Mexico, the western Gulf of Mexico, Campeche Bay in the southern Gulf of Mexico, and the Bahamas. Pairwise estimates of genetic divergence between sharks in the Bahamas and those in all other localities were more than an order of magnitude higher than between pairwise comparisons involving the other localities. Demographic modelling indicated that sharks in all five regions diverged after the last glacial maximum and, except for the Bahamas, experienced post-glacial, population expansion. The patterns of genetic variation also suggest that the southern Gulf of Mexico may have served as a glacial refuge and source for the expansion. Results of the study demonstrate that barriers to gene flow and historical genetic demography contributed to contemporary patterns of population structure in a coastal migratory species living in an otherwise continuous marine habitat. The results also indicate that for many marine species, failure to properly characterize barriers in terms of levels of contemporary gene flow could in part be due to inferences based solely on equilibrium assumptions. This could lead to erroneous conclusions regarding levels of connectivity in species of conservation concern.

While much attention has been paid to the climatic controls of species’ range limits, other factors such as dispersal limitation are also important. Temperature is an important control of the distribution of coastal mangrove forests, and mangrove expansion at multiple poleward range limits has been linked to increasing temperatures. However, mangrove abundances at other poleward range limits have been surprisingly insensitive to climate change, indicating other drivers of range limitation. For example, along the west coast of North America, the poleward mangrove range limits are found on the Baja California and mainland coasts of Mexico, between 26.8 - 30.3°N. Non-climatic factors may play an important role in setting these range limits as 1) the abundance of range limit populations has been relatively insensitive to climate variability and 2) an introduced population of mangroves has persisted hundreds of kilometers north of the natural range limits. We combined a species distribution model with a high-resolution oceanographic transport model to identify the roles of climate and dispersal limitation in controlling mangrove distributions. We identified estuarine habitat that is likely climatically suitable for mangroves north of the current range limits. However, propagules from current mangrove populations are unlikely to reach these suitable locations due to prevailing ocean currents and geomorphic factors that create a patchy distribution of estuarine habitat with large between-patch distances. Thus, although climate change is driving range shifts of mangroves in multiple regions around the world, dispersal is currently limiting poleward mangrove expansion at several range limits, including the west coast of North America. Methods Particle transport simulation Propagule trajectories were computed using surface-ocean current data from a mesoscale and tide-resolving configuration of the Massachusetts Institute of Technology general circulation model (MITgcm). The simulation was carried out in a latitude-longitude-polar cap (LLC) configuration with a polar cap that has 4320 grid cells on each side (hereafter referred to as LLC4320). There are 243 million horizontal grid cells and 90 vertical (depth) levels for a total grid count of 2.2 ^ 1010. The model has a nominal horizontal grid resolution of 1/48°, which ranges from 0.75 km near Antarctica to 2.2 km at the Equator, and a vertical grid spacing of 1 m near the surface to better resolve surface currents and diurnal cycles. A Lagrangian approach was used to compute particle propagation by linearly interpolating the zonal and meridional LLC4320 surface-ocean velocities and using a first-order Euler time-stepping method. Vertical motion was neglected, which is a reasonable assumption for mangrove propagules that are buoyant and generally remain on the ocean surface. Release locations were generated from the mangrove extent data described above. Release locations were shifted to the closest ocean grid cell (hereafter called ‘coastal grid cells’) and potential duplicate locations removed. Particles were released hourly at 589 coastal grid cells from 13 September 2011 to 13 November 2011 (i.e., 1,448 time steps in total), which coincides with the period of reported propagule availability in the region. Simulated propagules were tracked over 12 months, which was the maximum floating period considered. From the Lagrangian particle trajectories, dispersal trajectory density maps were generated by aggregating all modeled particle trajectories on a 1/48° resolution grid (i.e., the native grid resolution). We then tracked all the particles that stranded, i.e., reached an ocean cell adjacent to a land grid cell within the respective floating period. To account for the role of habitat suitability in our assessment of mangrove range limit dynamics in the region, we combined dispersal simulations with our coastal wetland layer. More specifically, we susbetted the strandings that were in grid cells potentially suitable for mangrove establishment and growth, i.e., either a saltmarsh or mangrove cell.

This study examines how population change is associated with changes in sociodemographics and economic outcomes across diverse geographic contexts in the United States from 2000 to 2020. Using Census Tract-level data and generalized additive models (GAMs), we found that communities experiencing population growth showed significant improvements in socioeconomic indicators: for example, a 50% population increase in Northeast metropolitan non-coastal areas was associated with a $10,062 rise [95% confidence interval (CI) = $9,181, $10,944] in median household income. Conversely, areas with population decline faced increasing challenges to community composition: communities experiencing a 50% population decline in West coastal metropolitan areas saw their median age increase by 2.556 years (95% CI = 2.23, 2.89 years), indicating an accelerated aging population. We observed a positive relationship between population growth and local economic growth, with areas experiencing population decline or slow growth showing below-average economic growth. While population change alone explained 10.1% of the variance in county-level GDP growth, incorporating sociodemographic shifts alongside population change using a partial least squares regression (PLSR) more than doubled the explanatory power to 21.4%. Overall, we often found the strength of relationships and sometimes the direction varied by geographic context: coastal areas showed distinct patterns from inland regions, and metropolitan areas responded differently than rural ones. For instance, the percentage of owner-occupied housing was negatively associated with population growth in metropolitan areas, but positively associated in non-metropolitan areas. Our research provides valuable insights for policymakers and planners working to address community changes, particularly in the context of anticipated climate-induced migration. The results suggest that strategies for maintaining economic vitality need to consider not just population retention, but also demographic profiles and socioeconomic opportunities across different geographic contexts.

NOAA Fisheries and its partners conduct fisheries-independent surveys in 8 regions in the US (Northeast, Southeast, Gulf of Mexico, West Coast, Gulf of Alaska, Bering Sea, Aleutian Islands, Hawai’i Islands). These surveys are designed to collect information on the seasonal distribution, relative abundance, and biodiversity of fish and invertebrate species found in U.S. waters. Over 900 spe...