Cultural and Environmental Predictors of Pre-European Deforestation on Pacific Islands

Abstract

The varied islands of the Pacific provide an ideal natural experiment for studying the factors shaping human impact on the environment. Previous research into pre-European deforestation across the Pacific indicated a major effect of environment but did not account for cultural variation or control for dependencies in the data due to shared cultural ancestry and geographic proximity. The relative importance of environment and culture on Pacific deforestation and forest replacement and the extent to which environmental impact is constrained by cultural ancestry therefore remain unexplored. Here we use comparative phylogenetic methods to model the effect of nine ecological and two cultural variables on pre-European Pacific forest outcomes at 80 locations across 67 islands. We show that some but not all ecological features remain important predictors of forest outcomes after accounting for cultural covariates and non-independence in the data. Controlling for ecology, cultural variation in agricultural intensification predicts deforestation and forest replacement, and there is some evidence that land tenure norms predict forest replacement. These findings indicate that, alongside ecology, cultural factors also predict pre-European Pacific forest outcomes. Although forest outcomes covary with cultural ancestry, this effect disappears after controlling for geographic proximity and ecology. This suggests that forest outcomes were not tightly constrained by colonists’ cultural ancestry, but instead reflect a combination of ecological constraints and the short-term responses of each culture in the face of those constraints.

Cultural macroevolution matters

“…Thus, there is no overcounting or undercounting of evolutionary events. Phylogenetic methods have recently been used to make inferences about things such as the ancestral state of postmarital residence patterns in Austronesian cultures (44), the evolution of political complexity (45), the effects of cultural ancestry on deforestation (46), and the links between cattle and matrilinity (47). Mark Pagel and Andrew Meade introduced a method called "Discrete" in the program BayesTraits that models the evolution of two binary traits and tests between dependent and independent models of evolution (48,49).…”

Invasive alien species on islands: impacts, distribution, interactions and management

“…Islands have a long history of over-exploitation (Atkinson et al 2016), with Easter Island being a stark example of the ecological collapse that can follow (Brander & Taylor 1998). IASs both interact with and benefit from over-exploitation of native species.…”

Examining the Sustainability of Tropical Island Forests: Advances and Challenges in Measurement, Monitoring, and Reporting in the U.S. Caribbean and Pacific

“…Therefore, we examined the islands' forests according to the Holdridge Life Zones system, which can be used as a proxy for ecosystem or community type). Most of these islands were nearly completely to entirely forested prior to human occupation and many underwent some or, in many cases, a significant degree of forest conversion to agricultural and grazing lands, or to grasslands and badlands [36,37]. These land use changes occurred during periods of initial settlement, colonization, agricultural expansion, and related population growth, primarily on relatively accessible islands and those with more gently sloped terrain (e.g., the larger islands of Hawaii and Puerto Rico) [36][37][38][39][40][41].…”

“…Most of these islands were nearly completely to entirely forested prior to human occupation and many underwent some or, in many cases, a significant degree of forest conversion to agricultural and grazing lands, or to grasslands and badlands [36,37]. These land use changes occurred during periods of initial settlement, colonization, agricultural expansion, and related population growth, primarily on relatively accessible islands and those with more gently sloped terrain (e.g., the larger islands of Hawaii and Puerto Rico) [36][37][38][39][40][41]. Far less deforestation or conversion to other land uses, if any, occurred on the most isolated islands (e.g., those of Palau) or on those with forests on steep, rugged terrain and in very wet climates (e.g., Tutuila in American Samoa, high islands in eastern Micronesia).…”

“…Forested area in three Pacific jurisdictions is dominated by trees >28 cm dbh) attributed in part to the presence of coconut trees in forest plantations and agroforests [42]. 89 Many of the historically deforested island jurisdictions in the Caribbean and Pacific regions have since recovered a significant portion of once cleared forest areas through regeneration, planting, or both, mostly on agricultural lands that were abandoned with changes in socioeconomic dynamics tied to industrialization, urbanization, globalization, and other processes [37,38]. Some forest recovery also has occurred as a result of environmental legislation and conservation efforts [39].…”