Examples of the Historical Method in Action

Recently, a handful of papers have used some form of this historical-descriptive method to demonstrate evidence of species' responses to climate changes that have occurred over the last century. Barry et al.(1995) and Sagarin et al. (1999) documented a general increase in southern invertebrate species and a decrease in northern species between two investigations of a single intertidal site conducted 60 years apart. This faunal change was concomitant with an increase in mean annual shoreline ocean temperatures. Holbrook et al. (1997) found an overall decline in abundance and shift toward dominance of southern reef fish species in the Southern California Bight following a shift to warmer ocean temperatures in the mid-1970s. California Cooperative Oceanic Fisheries Investigations (CalCOFI) data have been used to document population increases and northward range expansion of sardine populations during multidecadal ocean warming since the mid-1970s (Lluch-Belda et al. 1992). Southward (1967, 1995) found that warm-water species in the English Channel increased in abundance and cold-water species declined during periods of ocean warming (1920-1960; 1981-1995) whereas the opposite occurred during a cooling period (1960-1981). Parmesan (1996) compared her extensive surveys of the Edith's checkerspot butterfly in western North America to historical records and found that its range has contracted northward and toward higher elevation with climate warming. These studies are consistent with predictions developed in earlier papers of poleward species range shifts or range contractions from the equator, although with the exception of Parmesan (1996), they offer indirect evidence by only looking at a limited area within species' ranges.

Other evidence seems to support different models for responses of species to climate change. Roemmich and McGowan (1995) suggested that warming of the surface layer in southern California coastal waters had increased stratification and prevented upwelling of more nutrient rich water.This model was supported by long-term oceanographic records and species collections from CalCOFI which showed a 70% decline in zooplankton in southern California since 1951, concurrent with sea surface warming of up to 1.5°C. This may also help to explain a 90% decline in sooty shearwater abundance and a 40% decline in seabird abundance overall in the California current between 1987 and 1994 (Veit et al. 1996, 1997).

The science of phenology, which focuses on timing of periodic biological events such as migration, egg laying, and leafing, has reemerged as a source of models and data for historical studies of species' responses to climate change. Sparks and Carey (1995) analyzed plant phenological records collected by seven generations of an English family since 1736 and found significant correlations between temperature and dates of first leafing, flowering, and appearance. This relationship was used to predict earlier dates for the phenological variables under proposed climate warming scenarios. Similar phenological models are supported for laying dates in U.K. birds, in which 20 of 65 species studied between 1971 and 1995 showed earlier laying dates, and only 1 species showed later laying dates (Crick et al. 1997), as well as for amphibians in England which showed progressively earlier spawning dates between 1978 and 1994, a period of climatic warming (Beebee 1995).

In this chapter, I defend the use of the historical-descriptive method in climate change studies, but also discuss shortcomings of the method itself, as well as potential problems with the types of data typically encountered in historical studies. These issues are discussed within the context of my research (with collaborators James P. Barry, Sarah E. Gilman, and Charles H. Baxter) on observed long-term (multidecadal) changes to the nearshore marine communities of the Hopkins Marine Station (HMS) in Pacific Grove, California, at the southern end of Monterey Bay (36°37.3'N, 121°54.3'W) (Fig. 3.1).

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  • ambrogio
    What are examples of historical method?
    8 years ago

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