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Roberts DK, Sarver DE, Cash AR, Walker BH, Lim CS. Understanding health behaviors that modify the risk for obesity in ADHD. J Pediatr Psychol 2024:jsae018. [PMID: 38516857 DOI: 10.1093/jpepsy/jsae018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/31/2024] [Accepted: 02/28/2024] [Indexed: 03/23/2024] Open
Abstract
OBJECTIVE Research provides support for the associated risk of inadequate sleep duration, limited physical activity, and excessive media use in attention-deficit/hyperactivity disorder (ADHD) and obesity. The present study aims to (1) examine the association between ADHD and overweight or obese status (OW/OB); (2) comprehensively examine sleep duration, physical activity, and media use as potential moderators of OW/OB; and (3) examine the moderating effects of these health behaviors cross-sectionally by comparing medicated youth with ADHD, unmedicated youth with ADHD, and youth without ADHD. METHODS Data were acquired from the 2018 and 2019 National Survey of Children's Health, a nationally representative survey of caregivers conducted across the United States. The current study used data for youth 11-17 years old with a final sample size of 26,644. Hours of sleep, physical activity, and media use per day were dichotomized based on national recommendation guidelines for each health behavior (i.e., either meeting or not meeting guidelines). RESULTS The OW/OB prevalence rate was 7% greater among unmedicated youth with ADHD than among medicated youth with ADHD. Medicated youth with ADHD and peers without ADHD had similar OW/OB rates. Among medicated youth with ADHD, physical activity, sleep duration, and media use did not contribute to OW/OB risk after controlling for family poverty level. However, among unmedicated youth with ADHD, meeting sleep duration guidelines was linked to a lower OW/OB risk. CONCLUSION Overall, findings suggest that clinical providers and parents may wish to prioritize improved sleep duration in the management of OW/OB risk in youth with ADHD.
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Affiliation(s)
- Delanie K Roberts
- Department of Psychology, Children's Hospital of Los Angeles, Los Angeles, CA, United States
| | - Dustin E Sarver
- Department of Psychiatry and Human Behavior, Center for Advancement of Youth, University of Mississippi Medical Center, Jackson, MS, United States
- Department of Pediatrics, Center for Advancement of Youth, University of Mississippi Medical Center, Jackson, MS, United States
| | - Annah R Cash
- Department of Psychology, Child Study Center, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
| | - Benjamin H Walker
- Department of Population Health, University of Mississippi Medical Center, Jackson, MS, United States
| | - Crystal S Lim
- Department of Health Psychology, University of Missouri, Columbia, MO, United States
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Brown DC, Lariscy JT, Walker BH. State-Level Trends in Lifespan Variability in the United States, 1960-2019: A Research Note. Demography 2023; 60:1-14. [PMID: 36692169 DOI: 10.1215/00703370-10423884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
State-level disparities in life expectancy are wide, persistent, and potentially growing in the United States. However, the extent to which differences in lifespan variability by state have changed over time is unclear. This research note describes trends in lifespan variability for the United States overall and by state from 1960 to 2019 using period life table data from the United States Mortality Database. Lifespan disparity at birth (e0†) decreased over time in the United States overall from 14.0 years in 1960-1964 to 12.2 in 2015-2019. Lifespan variability decreased in all states, but states differed in the level and pace with which these changes occurred. Southern states and the District of Columbia exhibited consistently higher (i.e., less equitable) levels of lifespan variability than the nation overall. Conversely, lifespan variability was lower among several states in the Northeast (e.g., Connecticut and Massachusetts), Upper Midwest (e.g., Iowa, Minnesota, and Wisconsin), and West (e.g., California, Oregon, Utah, and Washington). We observe a particularly worrisome trend of increasing lifespan variability for the United States overall and for most states from 2010-2014 to 2015-2019. Monitoring state-level trends in lifespan variability has the potential to inform policies designed to ameliorate population health disparities.
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Affiliation(s)
- Dustin C Brown
- Department of Sociology and Social Science Research Center, Mississippi State University, Mississippi State, MS, USA
| | - Joseph T Lariscy
- Department of Sociology, University of Memphis, Memphis, TN, USA
| | - Benjamin H Walker
- Department of Population Health Science, John D. Bower School of Population Health, University of Mississippi Medical Center, Jackson, MS, USA
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Walker BH, Brown DC, Walker CS, Stubbs-Richardson M, Oliveros AD, Buttross S. Childhood adversity associated with poorer health: Evidence from the U.S. National Survey of Children's Health. Child Abuse Negl 2022; 134:105871. [PMID: 36095924 DOI: 10.1016/j.chiabu.2022.105871] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 07/22/2022] [Accepted: 08/31/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND The association between adverse childhood experiences (ACEs) and increased risk of health problems is well established. However, many studies have relied on unrepresentative or high-risk samples and have focused on a narrow range of health problems. Prior research assessing potential age differences in the ACE-health connection is also sparse. OBJECTIVE To comprehensively examine the extent to which ACEs are associated with physical, mental, and neurodevelopmental health outcomes in childhood and assess whether these associations differ between age groups. PARTICIPANTS & SETTING Pooled cross-sectional data from the 2016-2019 National Survey of Children's Health (N = 98,732). METHODS We estimated age-stratified binary logistic regression models examining associations between the number of ACEs and physical, mental, and neurodevelopmental health problems net of sociodemographic and socioeconomic controls. Separate models were estimated for the total population (ages 3-17), early childhood (ages 3-5), middle childhood (ages 6-11), and adolescence (ages 12-17). RESULTS We observed a dose-response relationship between ACE exposure and childhood physical, mental, and neurodevelopmental health problems in all age groups. The largest disparities exist between children with no ACEs and three or more ACEs. Compared to children without ACEs, children with three or more ACEs had significantly higher adjusted odds of externalizing disorders (OR = 4.40), internalizing disorders (OR = 5.13), neurodevelopmental disorders (OR = 2.40), and physical health problems (OR = 2.08). CONCLUSIONS Our results add to evidence linking ACEs to childhood health disparities. Further, findings indicate that ACEs have persistent negative effects across age groups and that clinicians should monitor ACEs when assessing children's physical, mental, and neurodevelopmental health at any age.
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Affiliation(s)
- Benjamin H Walker
- Department of Population Health Science, John D. Bower School of Population Health, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39212, United States of America.
| | - Dustin C Brown
- Department of Sociology, Mississippi State University, Bowen Hall, 456 Hardy Road, Mississippi State, MS 39762, United States of America; Social Science Research Center, Mississippi State University, 1 Research Blvd, Suite 103, Starkville, MS 39759, United States of America
| | - Courtney S Walker
- Department of Psychiatry, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39212, United States of America
| | - Megan Stubbs-Richardson
- Social Science Research Center, Mississippi State University, 1 Research Blvd, Suite 103, Starkville, MS 39759, United States of America
| | - Arazais D Oliveros
- Department of Psychology, Mississippi State University, PO Box 6161, 202 Magruder Hall, Mississippi State, MS 39762, United States of America
| | - Susan Buttross
- Department of Pediatrics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39212, United States of America
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Walker BH, Brown DC. Trends in lifespan variation across the spectrum of rural and urban places in the United States, 1990–2017. SSM Popul Health 2022; 19:101213. [PMID: 36059373 PMCID: PMC9434220 DOI: 10.1016/j.ssmph.2022.101213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 07/17/2022] [Accepted: 08/16/2022] [Indexed: 12/03/2022] Open
Abstract
Mortality disparities between urban and rural areas in the United States widened in recent decades as mortality improvements in rural areas slowed. Although the existence of a rural mortality penalty is well-documented, previous research in this area has focused almost exclusively on differences in average levels of mortality between rural and urban areas rather than differences in levels of lifespan variation within rural and urban areas. This oversight is important because monitoring trends in lifespan variation provides unique insights into levels of inequality in the age-at-death distribution within a population. Does the rural mortality penalty in life expectancy extend to lifespan variation? We used U.S. Multiple Cause of Death data files to measure life disparity at birth (e0†) from 1990 to 2017. We found that the rural mortality penalty extends to lifespan variation as large metropolitan areas had greater improvements in life disparity than nonmetropolitan areas. Beginning around 2011, all areas began to show increased life disparity with the largest increases occurring in nonmetropolitan areas. Age decomposition results showed that the nonmetropolitan increases were due to rising working-age mortality. Greater variability in the age-at-death distribution represents an additional dimension of inequality for Americans living in rural places. Improvements in metropolitan mortality beginning in the early 1990s resulted in a growing rural mortality penalty Recent increases in working-age mortality have contributed to the rural mortality penalty. Life expectancy improvements in metropolitan areas are associated with a decrease in lifespan variation. Greater lifespan inequality represents an additional dimension of inequality for rural Americans.
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Walker CS, Walker BH, Brown DC, Buttross S, Sarver DE. Defining the role of exposure to ACEs in ADHD: Examination in a national sample of US children. Child Abuse Negl 2021; 112:104884. [PMID: 33360863 DOI: 10.1016/j.chiabu.2020.104884] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/21/2020] [Accepted: 12/04/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Clinical presentations of ADHD vary according to biological and environmental developmental influences. An emerging field of research has demonstrated relationships between exposure to adverse childhood experiences (ACEs) and ADHD prevalence, particularly in high-risk samples. However, research examining the combined role of traditional risk factors of ADHD and ACEs is limited, and reliance on high-risk samples introduces sampling bias. OBJECTIVE To examine the influence of ACEs on ADHD diagnosis using a large, nationally representative sample of US children. PARTICIPANTS AND SETTING Nationally representative samples (2017 and 2018) of 40,075 parents from the National Survey of Children's Health (NSCH). METHODS We conducted logistic regression models to examine the association of ACEs and ADHD diagnosis, controlling for child and parent demographic variables and other risk factors. RESULTS Exposure to ACEs was significantly associated with parent-reported ADHD diagnosis, controlling for known parental and child-risk factors of ADHD. The association followed a gradient pattern of increased ADHD prevalence with additional exposures. Compared to children with no ACEs, the odds of an ADHD diagnosis were 1.39, 1.92, and 2.72 times higher among children with one, two and three or more ACEs. The ACE most strongly associated with the odds of ADHD was having lived with someone with mental illness closely followed by parent/guardian incarceration. CONCLUSIONS Results further strengthen the evidence that ACEs exposure is associated with increased ADHD prevalence. Clinicians should assess ACEs in the diagnosis of ADHD. Furthermore, results of the study lend support to the efforts of agencies (both institutional and state-level) promoting routine screening of ACEs in children.
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Affiliation(s)
| | - Benjamin H Walker
- Social Science Research Center, Mississippi State University, United States
| | - Dustin C Brown
- Social Science Research Center, Mississippi State University, United States; Department of Sociology, Mississippi State University, United States
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Shope TR, Walker BH, Aird L, Southward L, Martin JM. Influenza Vaccine Requirements in United States Child Care Centers. J Pediatric Infect Dis Soc 2020; 9:566-572. [PMID: 31828319 DOI: 10.1093/jpids/piz078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 10/18/2019] [Indexed: 11/14/2022]
Abstract
BACKGROUND Influenza vaccine is the most effective means to prevent influenza for the high-risk population of child care attendees. This national survey assessed child care center directors' reports of seasonal influenza vaccine requirements for children and adult caregivers. METHODS This was a 2016 telephone-based survey of child care center directors randomly selected from a national database of licensed United States child care centers and queried about influenza vaccine requirements. Conceptually related items were grouped into 4 indexes: general infection control, use of health consultants, quality of child care, and pandemic influenza preparedness. These indexes, along with other center and director characteristics, were used to predict director-reported influenza vaccine requirements. RESULTS Of 518 child care center directors, only 24.5% and 13.1% reported an influenza vaccine requirement for children and adult caregivers, respectively. Center and director characteristics and the indexes were not associated with a director-reported influenza vaccine requirement. After adjusting for covariates, only having a state influenza vaccine law for children and an adult influenza vaccine requirement predicted having a child influenza vaccine requirement. Only having a child influenza vaccine requirement predicted having an adult vaccine requirement. CONCLUSIONS Director-reported influenza vaccine requirements for children and adult caregivers were influenced primarily by state influenza vaccine laws. Given the high risk of children in child care and low director-reported influenza vaccine requirements, more states should pass laws requiring influenza vaccine for children and adult caregivers at child care programs.
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Affiliation(s)
- Timothy R Shope
- Division of General Academic Pediatrics, Department of Pediatrics, University of Pittsburgh School of Medicine, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Benjamin H Walker
- Social Science Research Center, Mississippi State University, Starkville, Mississippi, USA
| | - Laura Aird
- Department of Healthy, Resilient Children, Youth, and Families, American Academy of Pediatrics, Itasca, Illinois, USA
| | - Linda Southward
- Social Science Research Center, Mississippi State University, Starkville, Mississippi, USA
| | - Judith M Martin
- Division of General Academic Pediatrics, Department of Pediatrics, University of Pittsburgh School of Medicine, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Shope TR, Walker BH, Aird LD, Southward L, McCown JS, Martin JM. Pandemic Influenza Preparedness Among Child Care Center Directors in 2008 and 2016. Pediatrics 2017; 139:peds.2016-3690. [PMID: 28562271 DOI: 10.1542/peds.2016-3690] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/06/2017] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Children in child care centers represent an important population to consider in attempts to mitigate the spread of an influenza pandemic. This national survey, conducted in 2008 and 2016, assessed directors' reports of their child care centers' pandemic influenza preparation before and after the 2009 H1N1 novel influenza pandemic. METHODS This was a telephone-based survey of child care center directors randomly selected from a national database of licensed US child care centers who were queried about their preparedness for pandemic influenza. We grouped conceptually related items in 6 domains into indexes: general infection control, communication, seasonal influenza control, use of health consultants, quality of child care, and perceived barriers. These indexes, along with other center and director characteristics, were used to predict pandemic influenza preparedness. RESULTS Among 1500 and 518 child care center directors surveyed in 2008 and 2016, respectively, preparation for pandemic influenza was low and did not improve. Only 7% of directors had taken concrete actions to prepare their centers. Having served as a center director during the 2009 influenza pandemic did not influence preparedness. After adjusting for covariates, child care health consultation and years of director's experience were positively associated with pandemic influenza preparation, whereas experiencing perceived barriers such as lack of knowing what to do in the event of pandemic influenza, was negatively associated with pandemic influenza preparedness. CONCLUSIONS Pandemic influenza preparedness of child care center's directors needs to improve. Child care health consultants are likely to be important collaborators in addressing this problem.
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Affiliation(s)
- Timothy R Shope
- Division of General Academic Pediatrics, Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania;
| | - Benjamin H Walker
- Social Science Research Center, Mississippi State University, Starkville, Mississippi; and
| | - Laura D Aird
- Department of Child Health and Wellness, American Academy of Pediatrics, Elk Grove Village, Illinois
| | - Linda Southward
- Social Science Research Center, Mississippi State University, Starkville, Mississippi; and
| | - John S McCown
- Social Science Research Center, Mississippi State University, Starkville, Mississippi; and
| | - Judith M Martin
- Division of General Academic Pediatrics, Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania
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Walker BH, McCown JS, Bowser D, Patev A, Raede FS, Razavi M, Dzielak D, Southward LH. An assessment of emergency department use among Mississippi's Medicaid population. J Miss State Med Assoc 2015; 56:120-124. [PMID: 26182673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
BACKGROUND National trends in Emergency Department (ED) use suggest Medicaid recipients visit the ED more frequently and make more non-emergent ED visits than those uninsured and privately insured. Given the absence of data on Medicaid beneficiaries in Mississippi, it is important to explore their ED utilization, particularly frequent and non-emergent ED visits. METHOD Medicaid claims data were used to calculate ED visit rates and identify common diagnoses within the Mississippi Medicaid population. Non-emergent ED visits were classified using the NYU ED algorithm. RESULTS In 2012, 605,555 ED claims were made by 290,324 Medicaid beneficiaries in Mississippi, representing 43.7% of the Medicaid population (664,583). Twelve percent of ED users were frequent users (4 or more claims per year). Most claims (57.5%) were non-emergent, meaning they could have been treated in a primary care setting. CONCLUSION High rates of non-emergent ED visits suggest gaps in primary care delivery for Mississippi Medicaid beneficiaries.
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Walker BH, Sinclair HC, MacArthur J. Social norms versus social motives: the effects of social influence and motivation to control prejudiced reactions on the expression of prejudice. Social Influence 2014. [DOI: 10.1080/15534510.2014.904247] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Walker BH, Mattfeldt-Beman MK, Tomazic TJ, Sawicki MA. Provision of nutrition counseling, referrals to registered dietitians, and sources of nutrition information among practicing chiropractors in the United States. J Am Diet Assoc 2000; 100:928-33. [PMID: 10955051 DOI: 10.1016/s0002-8223(00)00267-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To investigate US chiropractors' provision of nutrition counseling and referrals to registered dietitians and sources of nutrition information. Chiropractors' perceptions of the minimum educational requirement for registered dietitians and nutrition training received in chiropractic school were also examined. DESIGN A descriptive study was conducted by use of a nationwide, mailed survey. SUBJECTS/SETTING Surveys were sent to 1,590 practicing chiropractors in the United States, selected randomly from The National Directory of Chiropractic. Of the 410 responses received, 375 were usable (response rate = 23.6%). STATISTICAL ANALYSIS Descriptive statistics were used to summarize data along with the Pearson chi 2 test and Kendall tc rank correlation to determine associations for categorical questions. RESULT Nearly 90% of respondents provided nutrition counseling to their patients, even though the majority believed that they were inadequately trained in nutrition. One-on-one dietary instruction was the most common method of providing nutrition counseling, and supplement use was the most common health-related situation/condition for which nutrition counseling was used. Most respondents did not correctly select the minimum educational requirement for registered dietitians, did not refer patients to registered dietitians, and did not use registered dietitians as a source of nutrition information. Nevertheless, 65% of respondents anticipated increased collaborations between registered dietitians and chiropractors. APPLICATIONS/CONCLUSIONS Chiropractors provide nutrition counseling to a large number of patients each year; thus, they have the potential to substantially affect patients' nutritional status. There is a clear need and opportunity for registered dietitians to collaborate with chiropractors.
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Affiliation(s)
- B H Walker
- Department of Nutrition and Dietetics, Saint Louis University, Mo., USA
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Sala OE, Chapin FS, Armesto JJ, Berlow E, Bloomfield J, Dirzo R, Huber-Sanwald E, Huenneke LF, Jackson RB, Kinzig A, Leemans R, Lodge DM, Mooney HA, Oesterheld M, Poff NL, Sykes MT, Walker BH, Walker M, Wall DH. Global biodiversity scenarios for the year 2100. Science 2000; 287:1770-4. [PMID: 10710299 DOI: 10.1126/science.287.5459.1770] [Citation(s) in RCA: 3015] [Impact Index Per Article: 125.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.
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Affiliation(s)
- O E Sala
- Department of Ecology and Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura, Faculty of Agronomy, University of Buenos Aires, Avenida San Martín 4453, Buenos Aires 1417, Argentina.
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Sala OE, Chapin FS, Armesto JJ, Berlow E, Bloomfield J, Dirzo R, Huber-Sanwald E, Huenneke LF, Jackson RB, Kinzig A, Leemans R, Lodge DM, Mooney HA, Oesterheld M, Poff NL, Sykes MT, Walker BH, Walker M, Wall DH. Global biodiversity scenarios for the year 2100. Science 2000; 287:1770-1774. [PMID: 10710299 DOI: 10.1126/scince.287.5459.1770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.
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Affiliation(s)
- O E Sala
- Department of Ecology and Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura, Faculty of Agronomy, University of Buenos Aires, Avenida San Martín 4453, Buenos Aires 1417, Argentina.
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Affiliation(s)
- G C Daily
- Center for Conservation Biology, Department of Biological Sciences, Stanford University, California 94305-5020, USA
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Walker BH, Mcfarlane FR, Langridge JL. Grass Growth in Response to Time of Rainfall and Season Along a Climate Gradient in Australian Rangelands. Rangel J 1997. [DOI: 10.1071/rj9970095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Percentage green leaf and height of the major perennial grass species was estimated fortnightly at six locations along a rainfall predictability gradient from Katherine (most predictable) to Lake Mere near Cobar (aseasonal), and regressed on estimated plant available soil moisture (PASM) and time of year (T). Green leaf is more strongly related to T at Katherine and to PASM at Lake Mere with the other sites in-between. Differences between species in terms of seasonal growth phenology were minor, at all sites, and there were no meaningful patterns in percentage contributions by the species to sward biomass. A strong inter-seasonal rainfall pattern over the period of the study may have masked phenological differences between species, but it is also possible that changes in species composition very soon after livestock were introduced resulted in a decline in phenological differentiation. Whatever the reason, the differences observed in this study would ~ot warrant their use in the formulation of management strategies.
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Walker BH. Lens Design for the Near IR … Correction of Primary Chromatic Aberration. Appl Opt 1995; 34:8072-8073. [PMID: 21068915 DOI: 10.1364/ao.34.008072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The dispersion characteristic of conventional optical glass types will vary as a function of the wavelength region being considered. In the 1.0 to 1.5 µm region, the dispersion of traditional crown and flint glass types is found to be nearly the same. This results in a unique condition when attempting a lens design solution for this spectral region. A typical example is described here that will be helpful in understanding this phenomenon.
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Walker BH. Estimating secondary color. Appl Opt 1993; 32:7124. [PMID: 20856581 DOI: 10.1364/ao.32.007124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Image quality of a refracting lens system often will be limited by residual secondary color. Information in this paper permits rapid determination of blur spot size, and resulting image quality degradation, due to secondary color for a refracting lens system that has been designed with normal optical glasses and is free of primary color (achromatic). Included here is a brief description of the basic theory involved and an example of how the plotted data are used.
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Abstract
The most important implications of this analysis for Australia's rangelands are: i) Better predictions of climate change, both in spatial resolution and degree of confidence, are needed to progress beyond a broad-scale analysis of possible effects. ii) Given that better projections of climate will become available, a "generic" rangelands model, incorporating a better understanding of system-level responses to changes in climate, atmospheric composition and management strategies, is needed to investigate the implications of global change. iii) Based on our current state of understanding, it seems as though the changes in Australia's rangelands will be within the capabilities of managers to cope, over at least the next several decades, provided they are made aware of the likely local and regional changes as predictions improve, and provided they adopt flexible management strategies.
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Ojima DS, Kittel TGF, Rosswall T, Walker BH. Critical Issues for Understanding Global Change Effects on Terrestrial Ecosystems. Ecol Appl 1991; 1:316-325. [PMID: 27755766 DOI: 10.2307/1941760] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Marked alterations in the Earth's environment have already been observed, and these presage even greater changes as the impact of human (i.e., land use and industrial) activities increases. Direct and indirect feedbacks link terrestrial ecosystems with global change, and include interactions affecting fluxes of water, energy, nutrients, and "greenhouse" gases and affecting ecosystem structure and composition. Community development can affect ecosystem dynamics by altering resource partitioning among biotic components and through changes in structural characteristics, thereby affecting feedbacks to global change. The response of terrestrial ecosystems to the climate-weather system is dependent on the spatial scale of the interactions between these systems and the temporal scale that links the various components. The International Geosphere-Biosphere Programme (IGBP), which was initiated by the International Council of Scientific Unions (ICSU) in 1986, has undertaken to develop a research plan to address a predictive understanding of how terrestrial ecosystem will be impacted by global changes in the environment and the potential feedbacks. The IGBP science plan, which incorporates established Core Projects and activities related to research on terrestrial ecosystem linkages to global change, includes the International Global Atmospheric Chemistry Project (IGAC); the Biospheric Aspects of the Hydrological Cycle (BAHC); the Global Change and Terrestrial Ecosystems (GCTE); Global Analysis, Integration, and Modelling (GAIM); IGBP Data and Information System (DIS); and IGBP Regional Research Centers (RRC). The coupling of research and policy communities for the purpose of developing mechanisms to adapt to these impending changes urgently needs to be established.
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Abbott PD, Walker BH. Amniotic fluid embolism: a syndrome of intravascular coagulation. South Med J 1970; 63:1357-60. [PMID: 5529110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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