Testing for a trend in a partially incomplete hurricane record

The record of annual counts of basinwide North Atlantic hurricanes is incomplete prior to 1946. This has restricted efforts to identify a long-term trend in hurricane activity to the postwar period. In contrast, the complete record of U.S. landfalling hurricanes extends back to 1930 or earlier. Under the assumption that the proportion of basinwide hurricanes that make landfall is constant over time, it is possible to use the record of landfalling hurricanes to extend a test for trend in basinwide hurricane activity beyond the postwar period. This note describes and illustrates a method for doing this. The results suggest that there has been a significant reduction in basinwide hurricane activity over the period 1930-98.The record of annual counts of basinwide North Atlantic hurricanes is incomplete prior to 1946. This has restricted efforts to identify a long-term trend in hurricane activity to the postwar period. In contrast, the complete record of U.S. landfalling hurricanes extends back to 1930 or earlier. Under the assumption that the proportion of basinwide hurricanes that make landfall is constant over time, it is possible to use the record of landfalling hurricanes to extend a test for trend in basinwide hurricane activity beyond the postwar period. This note describes and illustrates a method for doing this. The results suggest that there has been a significant reduction in basinwide hurricane activity over the period 1930-98

Testing for trend in North Atlantic Hurricane activity, 1900-98

The detection of a trend in hurricane activity in the North Atlantic basin has been restricted by the incompleteness of the record prior to 1946. In an earlier paper, the complete record of U.S. landfalling hurricanes was used to extend the period of analysis back to 1930. In this paper, a further extension is made back to 1900. In doing so, the assumption in the earlier paper of an exponential linear trend is relaxed and the trend is estimated nonparametrically. The results show no significant trend in basinwide hurricane activity over the period 1900-98

Interannual variability of Alexandrium fundyense abundance and shellfish toxicity in the Gulf of Maine

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 2843-2855, doi:10.1016/j.dsr2.2005.06.020.Six years of oceanographic surveys of Alexandrium fundyense concentrations in the Gulf of Maine are combined with shellfish toxicity records from coastal monitoring stations to assess covariations of these quantities on seasonal to interannual time scales. Annual mean gulf-wide cell abundance varies by less than one order of magnitude during the time interval examined (1993-2002). Fluctuations in gulf-wide annual mean cell abundance and shellfish toxicity are not related in a consistent manner. This suggests that interannual variations in toxicity may be regulated by transport and delivery of offshore cell populations, rather than the absolute abundance of the source populations themselves.We gratefully acknowledge the support of the US ECOHAB Program, sponsored by NOAA, NSF, EPA, NASA, and ONR

Goodness of fit of probability distributions for sightings as species approach extinction

Estimating the probability that a species is extinct and the timing of extinctions is useful in biological fields ranging from paleoecology to conservation biology. Various statistical methods have been introduced to infer the time of extinction and extinction probability from a series of individual sightings. There is little evidence, however, as to which of these models provide adequate fit to actual sighting records. We use L-moment diagrams and probability plot correlation coefficient (PPCC) hypothesis tests to evaluate the goodness of fit of various probabilistic models to sighting data collected for a set of North American and Hawaiian bird populations that have either gone extinct, or are suspected of having gone extinct, during the past 150 years. For our data, the uniform, truncated exponential, and generalized Pareto models performed moderately well, but the Weibull model performed poorly. Of the acceptable models, the uniform distribution performed best based on PPCC goodness of fit comparisons and sequential Bonferroni-type tests. Further analyses using field significance tests suggest that although the uniform distribution is the best of those considered, additional work remains to evaluate the truncated exponential model more fully. The methods we present here provide a framework for evaluating subsequent models. © 2008 Society for Mathematical Biology

Inferring species extinction: The use of sighting records

Accurate measures of extinction are needed in biodiversity monitoring and conservation management, but ascertaining the exact time at which a species became extinct is difficult since a small population may go undetected for many years. For little-studied species, often the only information available is historical sighting data. Several statistical tests have been developed which use this information to make inferences about a species' extinction. The increasing array of methods can present a daunting choice. We review the more frequently cited methods, for each model explaining its assumptions, the data required, the scenarios it was developed for and power considerations, if known. We provide guidance on selecting the most appropriate method for a particular sighting record. We give examples from the literature to show how the methods have been usefully applied across conservation research, informing conservation decision-making and extinction inference