Pristinity, degradation and replacement: The three dimensions of human impact on island vegetation

Valentí Rull

doi:10.1177/0309133320960992

Abstract

This paper presents three extreme examples of the potential consequences of human settlement on the vegetation of oceanic and continental islands. The Neotropical Pantepui continental archipelago of sky islands is an example of pristinity, due to the almost nonexistent human impact that results from the remoteness and inaccessibility of these islands as well as the lack of natural resources to exploit. Easter Island is used to illustrate total vegetation degradation by deforestation and the exhaustion of natural resources, which has transformed the island into badlands with no signs of recovery. The Azores Islands have been chosen to illustrate replacement as, after initial postsettlement deforestation and extractive practices, a further transformative phase consisting of creating an almost totally anthropogenic vegetation with mostly exotic species occurred. The paper describes in some detail the developments of each case and the historical context in which they took place using historical, archeological and paleoecological evidence. Many intermediate states are possible among these three extremes, which can be represented with a ternary diagram (the PDR diagram), which is useful for characterizing the state of each island or archipelago in terms of human impact on terrestrial ecosystems and informing conservation and restoration practices.

Highlights

Either oceanic or continental, have been described as “discrete habitats isolated from other habitats by inhospitable surroundings” (Gillespie & Clague, 2009), and have been especially sensitive to human settlement and the ensuing cultural developments
The contingent nature of these anthropogenic modifications has challenged the explanatory capacity of theoretical island biogeography models aimed at interpreting the island biotas in terms of a dynamic equilibrium between immigration and extinction over geological time scales (Borregaard et al, 2016)
This paper describes three case studies representing three extreme situations of human impact on island vegetation, namely, pristinity, degradation and replacement

Summary

Introduction

Either oceanic or continental, have been described as “discrete habitats isolated from other habitats by inhospitable surroundings” (Gillespie & Clague, 2009), and have been especially sensitive to human settlement and the ensuing cultural developments. This paper describes three case studies representing three extreme situations of human impact on island vegetation, namely, pristinity, degradation and replacement. The term “replacement” refers to the intentional anthropogenic substitution of the original species and communities by others (usually exotic), including planted forests, crops, pastures, gardened terrains and similar features. This paper combines historical, archaeological and paleoecological evidence to briefly explain each case study and summarizes the information into a graphical synthetic framework that may be useful in addressing the topic of human impact on island vegetation in a general fashion. The aim of this paper is to introduce a simple quantitative and easy to visualize parameter based on three extreme states (P, D and R) of island vegetation after major human impact, useful to be incorporated into global databases for a relatively fast and more complete appraisal of the status of island’s terrestrial ecosystems. The existing databases may benefit from the massive introduction of the PDR parameters proposed here as a quick diagnostic tool

Pantepui: pristinity

The Azores Islands: replacement ev

Findings

Acknowledgments ee