A new study by Simon Fraser University historical ecologists finds that Indigenous-managed forests -- cared for as "forest gardens" -- contain more biologically and functionally diverse species than surrounding conifer-dominated forests and create important habitat for animals and pollinators. The findings are published today in Ecology and Society.1

Ts'msyen and Coast Salish peoples' management practices challenge the assumption that humans tend to overturn or exhaust the ecosystems they inhabit. This research highlights how Indigenous peoples not only improved the inhabited landscape, but were also keystone builders, facilitating the creation of habitat in some cases. The findings provide strong evidence that Indigenous management practices are tied to ecosystem health and resilience.2

Forest gardens are a common management regime identified in Indigenous communities around the world, especially in tropical regions. Armstrong says the study is the first time forest gardens have been studied in North America -- showing how important Indigenous peoples are in the maintenance and defence of some of the most functionally diverse ecosystems on the Northwest Coast.

  • 1. According to researchers, ancient forests were once tended by Ts'msyen and Coast Salish peoples living along the north and south Pacific coast. These forest gardens continue to grow at remote archaeological villages on Canada's northwest coast and are composed of native fruit and nut trees and shrubs such as crabapple, hazelnut, cranberry, wild plum, and wild cherries. Important medicinal plants and root foods like wild ginger and wild rice root grow in the understory layers. "These plants never grow together in the wild," says Chelsey Geralda Armstrong, an SFU Indigenous Studies assistant professor and the study lead researcher. "It seemed obvious that people put them there to grow all in one spot -- like a garden. Elders and knowledge holders talk about perennial management all the time." … "It's no surprise these forest gardens continue to grow at archaeological village sites that haven't yet been too severely disrupted by settler-colonial land-use."
  • 2. "Human activities are often considered detrimental to biodiversity, and indeed, industrial land management has had devastating consequences for biodiversity," says Jesse Miller, study co-author, ecologist and lecturer at Stanford University. "Our research, however, shows that human activities can also have substantial benefits for biodiversity and ecosystem function. Our findings highlight that there continues to be an important role for human activities in restoring and managing ecosystems in the present and future."

Chelsey Geralda Armstrong, Jesse E. D. Miller, Alex C. McAlvay, Patrick Morgan Ritchie, Dana Lepofsky. Historical Indigenous Land-Use Explains Plant Functional Trait Diversity. Ecology and Society, 2021; 26 (2) DOI: 10.5751/ES-12322-260206

Human land-use legacies have long-term effects on plant community composition and ecosystem function. While ancient and historical land use is known to affect biodiversity patterns, it is unknown whether such legacies affect other plant community properties such as the diversity of functional traits. Functional traits are a critical tool for understanding ecological communities because they give insights into community assembly processes as well as potential species interactions and other ecosystem functions. Here, we present the first systematic study evaluating how plant functional trait distributions and functional diversity are affected by ancient and historical Indigenous forest management in the Pacific Northwest. We compare forest garden ecosystems - managed perennial fruit and nut communities associated exclusively with archaeological village sites - with surrounding periphery conifer forests. We find that forest gardens have substantially greater plant and functional trait diversity than periphery forests even more than 150 years after management ceased. Forests managed by Indigenous peoples in the past now provide diverse resources and habitat for animals and other pollinators and are more rich than naturally forested ecosystems. Although ecological studies rarely incorporate Indigenous land-use legacies, the positive effects of Indigenous land use on contemporary functional and taxonomic diversity that we observe provide some of the strongest evidence yet that Indigenous management practices are tied to ecosystem health and resilience.

Key words: Forest Gardens, Functional Diversity, Land-Use Legacies, Pacific Northwest, Plant Functional Traits

Fig. 5. Functional Diversity Measures between Forest Gardens and Periphery Forests.
Fig. 5. Functional Diversity Measures between Forest Gardens and Periphery Forests. - Comparisons of functional diversity at forest gardens and peripheral forests, functional divergence did not show a significant response to site history (P = 0.07).