About This Project

Kelp forests house fisheries species, store carbon and protect coasts, but marine heatwaves can wipe them out in one season. Our global study (Smith et al. 2024) showed heatwaves are driving kelp declines, especially at the warm edge of species' ranges. Why do some forests recover while others don't? We're combining decades of diver surveys from sites globally with satellite sea temperatures, to find out. I'll pinpoint which forests are most at risk and where recovery is seen.

Ask the Scientists

What is the context of this research?

In 2011, a marine heatwave (MHW) off Western Australia wiped out kelp forests along more than 100 km of coast, and they still haven't returned (Wernberg et al. 2016). Off California kelp vanished after MHWs (Rogers-Bennett & Catton 2019; Arafeh-Dalmau et al. 2019). These events are becoming longer and more frequent (Oliver et al. 2018), yet responses vary: some kelp forests collapse while others nearby persist or rebound. Our global study of 1,322 coastal areas found that heatwave damage to foundation species like kelp increases towards the warm edge of species' ranges (Smith et al. 2024). But we know little about what happens next: why do some forests and species recover while others don't? I will combine decades of diver surveys on kelp forests with satellite sea temperatures since the early 1980s. Statistical models will test how impacts vary across each species' thermal range, and survival analysis will reveal what speeds or stalls recovery after each heatwave.

What is the significance of this project?

A strong El Niño is now developing, bringing a high risk of marine heatwaves to many of the world's kelp coasts. Kelp forests support fisheries, tourism, carbon storage and coastal protection worth billions of dollars a year, yet managers cannot predict which forests will recover after a heatwave and which will be lost for good. Our recent global study (Smith et al. 2024) showed that intense summer heatwaves are driving declines in kelp and other foundation species, with the worst impacts at the warm edge of species' ranges. It also found places where kelp showed no response, hinting at resilience. This project builds on that work by adding more recent years of monitoring data and following the same sites through repeated heatwaves, so we can ask what happens next: which forests resist, which recover, and how quickly. The answers will help managers decide where to focus protection and restoration, and how long to wait before judging whether a forest is recovering.

What are the goals of the project?

My goal is to find out why some kelp forests resist or recover from marine heatwaves while others don't. Funds will pay for my time and for me to present at an international conference. Work runs from Dec 2026 to Oct 2027. My dataset covers almost 5 decades of diver surveys, updated annually from over 200 kelp monitoring sites across Europe, North America, Japan and Australia. I'll match each site to daily satellite sea surface temperatures to identify every heatwave it experienced. Controls are sites unaffected by heatwaves, and years at each site with no heatwaves. I'll track each kelp population through time, flagging declines and whether and how fast it recovered. Statistical models will test whether a site's position in its species' temperature range affects how hard it is hit, and survival analysis will reveal what speeds or stalls recovery. I'll select models by comparing alternatives, then verify them with diagnostic and robustness checks. Results will be published open access.