Southward decrease in the protection of persistent giant kelp forests in the northeast Pacific

Nur Arafeh-Dalmau,Fiorenza Micheli,Hugh P Possingham,Kyle C Cavanaugh,Kate Cavanaugh,Gabriela Montaño-Moctezuma,Adrian Munguia-Vega,Tom W Bell

doi:10.1038/s43247-021-00177-9

Abstract

Kelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known. Here, we present a 35-year time series of high-resolution satellite imagery that maps the distribution and persistence of giant kelp (Macrocystis pyrifera) forests along ten degrees of latitude in the Northeast Pacific Ocean. We find that although 7.7% of giant kelp is protected by marine reserves, when accounting for persistence only 4% of kelp is present and protected. Protection of giant kelp decreases southerly from 20.9% in Central California, USA, to less than 1% in Baja California, Mexico, which likely exacerbates kelp vulnerability to marine heatwaves in Baja California. We suggest that a two-fold increase in the area of kelp protected by marine reserves is needed to fully protect persistent kelp forests and that conservation of climate-refugia in Baja California should be a priority.

Highlights

Kelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known
This transboundary region has recently been subject to extreme marine heatwaves that resulted in the loss of entire kelp forests[23,24], threatening the outcomes of conservation efforts that established a network of marine protected areas in California[25] and community-based marine reserves in Baja California[26]
Central California has the highest amount of persistent kelp forest found in the Northeast Pacific Ocean (34.8%), while Northern Baja California has the lowest (13.5%) (Fig. 1b)

Summary

Introduction

Kelp forests are globally important and highly productive ecosystems, yet their persistence and protection in the face of climate change and human activity are poorly known. Hypoxic events, and other extreme episodes are becoming more frequent and severe[15], ensuring the long-term persistence of species and ecosystems requires areabased conservation and adaptive strategies to address ongoing changes in climate and ocean chemistry[16]. One such strategy is protecting potential climate-refugia[17], areas where the impacts of climate change may be less severe[18]. We suggest that protection targets should increase by over two-fold the area required to protect present kelp in any given year

Methods

Results

Conclusion