History for ecologists: Biases and best practices in the use of nautical charts to understand long-term change to kelp.

Authors

Ursula Dhillon, Loren McClenachan

Published in

Annals of botany. Jul 10, 2026. Epub Jul 10, 2026.

Abstract

As coastal ecosystems and their associated ecosystem services are degraded, the value of historical baselines to understanding long-term dynamics has become clear. For kelp forests, a variety of historical sources is available to reconstruct ecological baselines, yet the limitations and possibilities of using these sources have not been adequately considered, leaving ecologists at risk of making critical errors of interpretation. Methods: Here, we identify historical contexts and types of historical sources that can be used to understand long-term change for kelp. We focus on one key source type, nautical charts, to identify temporal and spatial biases that should be considered in constructing baselines for kelp.
Spatial biases include a historical focus on charting regions of strategic interest, such as trading ports, as well as preferential representation in locations where kelp served as a waypoint for navigation for sailors. As a result, kelp on charts represents presence, not absence, and it cannot provide meaningful insight into the extent or density of historical kelp beds. Temporal biases also exist. Kelp was recorded on charts beginning in the 1850s, and is most useful to identify kelp until the 1910s. Surveys were only conducted in years of strategic need, with seasonality also affecting the degree to which extant kelp was recorded. Importantly, reprinting practices make it difficult to decipher whether indicated kelp is representative of a given year, and preclude the use of charts to establish time series of kelp.
To overcome these inherent biases, we provide a list of best practices for using these sources to understand baselines for kelp. This work demonstrates that there is a rich set of source material available from which to assess changes in coastal ecosystems and the associated loss of ecosystem services, and we provide a template for ecologists doing similar work globally.

PMID:
42430192
Bibliographic data and abstract were imported from PubMed on 10 Jul 2026.

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