. The scientific study of biodiversity changes is, in historical terms, relatively recent. It was mainly from the 1950s onwards, when the effects of human activity on the environment were already becoming evident, that data began to be systematically collected. This means that, in many cases, the only references available for conservation or restoration efforts come from ecosystems that were already altered. This raises a crucial question: how can we study the ecology of times when the human footprint on ecosystems was smaller?

In the Doñana Biological Station (EBD-CSIC), a research team addresses this challenge from the perspective of historical ecology, a field that draws on a wide range of historical, artistic and archaeological sources, to trace what biodiversity looked like in the past and how this knowledge can inform conservation policies today. In a new article published in Nature Reviews Biodiversity, the team identify eight types of historical sources that can help the scientific community gain valuable insights into species, ecosystems and how societies have interacted with nature. These sources include written documents, pictorial representations and traditional oral sources, among others.

“When we think about studying nature in the past, the first things that usually come to mind are analyzing archaeological remains or specimens kept in scientific collections. But many people are unaware of the potential of letters, paintings, old maps or oral traditions to shed light on changes in biodiversity and help design more informed conservation strategies”, explains Laetitia Navarro, researcher at the Doñana Biological Station and lead author of the study. 

What historical ecology reveals

This perspective provides fascinating examples from around the world. In Hawaii, for instance, combining data from archaeological sites and ethnographies and fishery reports revealed historical and contemporary periods of recovery in coral populations. In Southern Guinea, old aerial photographs, written materials and oral histories showed that forests and savannas expanded during 19th and 20th centuries, contradicting colonial narratives of massive deforestation, which guided land management policies. 

The combination of multiple sources can also help clarify species’ ecological histories. In Spain, the study of all kind of historical documents, cookbooks and geographical dictionaries revealed that the crayfish once thought to be native was actually introduced from Italy more than 400 years ago —forcing a reconsideration of current conservation strategies. Another example comes from Mexico, where oral tradition, historical documents and archaeological findings have made it possible to reconstruct nearly 300 years of fisheries of the East Pacific green turtle, a key piece of information to establish recovery targets for the species.

Beyond the historical value of these studies, integrating historical and cultural sources often allow researchers to identify the causes of ecological change over long periods of time and to guide restoration and conservation policies. In southwestern Canada, for example, the review of shell middens, archaeological remains, and oral sources revealed that most forest fires were intentionally set by Indigenous communities as a land management technique, leaving an ecological legacy on the composition and structure of the region.

The shifting baseline syndrome

“People tend to take as a reference of what a healthy nature looks like either what they have known throughout their lifetime or what their families have transmitted to them. But the passing of information across generations rarely goes further than grandparents, so, generation after generation, increasingly degraded ecosystems are accepted as the norm,” explains Laetitia Navarro.

This phenomenon, known as ecological amnesia or “shifting baseline syndrome”, has a huge influence on social expectations of conservation and current biodiversity policies. “Using a variety of sources to reconstruct long-term ecological knowledge can help us reconnect us with our natural heritage and sharpen our perception of biodiversity change”, said the researcher. 

The strength of greater dialogue between disciplines

New technologies will play a key role in the study and use of historical sources. Digitization and artificial intelligence will help uncover information on environmental and biodiversity issues that might otherwise have gone unnoticed in historical archives. This perspective fosters the development of interdisciplinary workflows that integrate various disciplines—such as history, ecology, and computer science—to digitize, share, and integrate historical biodiversity data.

Complementarily, citizen science can play an essential role in the identification and mobilization of historical biodiversity relevant-data, whether by contributing personal historical data such as old photographs, by participating in re-sampling projects like the Paisajes centenarios project, or by extracting historical data from digitized material on dedicated online platforms.

This publication is the result of SOURCES, a symposium and workshop organized at the Casa de la Ciencia in Seville in March 2023, as part of the European project SUMHAL, funded by the Spanish Ministry of Science and Innovation through the European Union’s ERDF funds. This symposium brought together experts in Conservation Biology, Ecology, History, Geography, and Paleobiology to discuss the multiple sources of historical information on biodiversity and the ways to integrate them into research and conservation.

“It was a truly interdisciplinary meeting, and we were able to see firsthand the many difficulties that exist for people researching in such diverse fields to cooperate,” says Miguel Clavero, researcher at the Doñana Biological Station – CSIC and co-author of the study. “But the search for common ground, although costly in terms of time and effort, allows us to generate long-term knowledge about nature and the role that people play in it—knowledge that is beyond the reach of studies conducted within the framework of a single discipline.”. 

Referencia científica

Laetitia M. Navarro, Chelsey Geralda Armstrong, Thomas Changeux, Dagmar Frisch, Graciela Gil-Romera, Dominik Kaim, Loren McClenachan, Catalina Munteanu, Péter Szabó, Viktor Baranov, Francisco Blanco-Garrido, J. Julio Camarero, María B. García, Molly Grace, Adam Izdebski, Naia Morueta-Holme, Francisco Pando, Rafael Schouten, Adam Spitzig, Jens-Christian Svenning, Anne-Sophie Tribot, Duarte S. Viana, Miguel Clavero. Integrating historical sources for long-term ecological knowledge and biodiversity conservation. Nature Reviews Biodiversity, https://doi.org/10.1038/s44358-025-00084-3