Biology subjects

Schoeman, D. S.

Publications and source records attributed to Schoeman, D. S..

5 recordsLinked to original sources

bioRxiv2025

Marine heatwaves drive range contraction and alternative states of kelp forests at their warm limit

Marine heatwaves are transforming ecosystems, yet their role in driving alternative states--and the conditions that enable these transitions--remains poorly understood. Using 30 years of satellite and underwater data, we assessed the impact of the 2014-2016 Pacific marine heatwaves on giant kelp forests (Macrocystis pyrifera) at their warm range limit in Mexico. By 2016, 88% of forests were lost, with limited recovery by 2023, including an 80 km range contraction at the southern edge. Surveys revealed three alternative states: replacement by heat-tolerant palm kelp (Eisenia arborea) in warmer regions; urchin barrens due to predator overfishing; and, unexpectedly, persistent giant kelp near the southern limit where high temperatures coincide with low human pressure. Pre-existing conditions, such as high urchin and palm kelp densities, shaped these outcomes. These findings show that responses to marine heatwaves are shaped by local ecological and human contexts, requiring tailored climate-adaptation strategies to promote resilience.

ecology↗

bioRxiv2024

Intensifying marine heatwaves and limited protection threaten global kelp forests

Kelp forests are one of the earths most productive ecosystems and are at the greatest risk from climate change, yet little is known regarding their future threats and current conservation status. By combining a global remote sensing dataset of floating kelp forests with climate data and projections, we find that exposure to projected marine heatwaves will increase [~]8 times compared to contemporary (2001-2020) exposure for intermediate climate scenarios. While exposure will intensify for all forests, climate refugia emerge for some southern hemisphere kelp forests, which have lower exposure to contemporary and projected marine heatwaves. Under these escalating threats, less than 3% of global kelp forests are currently within highly restrictive marine protected areas, the most effective conservation measure for providing climate resilience. Our findings emphasize the urgent need to increase the global protection of kelp forests and set bolder climate adaptation goals.

ecology↗

bioRxiv2024

Marine protected areas promote resilience of kelp forests to marine heatwaves by preserving trophic cascades

Under accelerating threats from climate change impacts, marine protected areas (MPAs) have been proposed as climate adaptation tools to enhance the resilience of marine ecosystems. Yet, debate persists as to whether and how MPAs may promote resilience to climate shocks. Here, we empirically assess whether a network of 85 temperate MPAs in coastal waters promotes resilience against marine heatwaves in Central and Southern California. We use 38 years of satellite-derived kelp cover to test whether MPAs enhance the resistance of kelp forest ecosystems to, and recovery from, the unprecedented 2014-2016 marine heatwave regime. We also leverage a 20-year time series of subtidal community surveys to understand whether protection and recovery of sea urchin predators within MPAs explain emergent patterns in kelp forest resilience through trophic cascades. We find that fully protected MPAs (i.e. no-take marine reserves) significantly enhance the resistance to and recovery of kelp forests to marine heatwaves in Southern California, but not in Central California. Differences in regional responses to the heatwaves may be partly explained by three-level trophic interactions comprising kelp, urchins, and predators of urchins. Urchin abundances in Southern California MPAs are significantly lower within fully protected MPAs during and after the heatwave, while the abundance of their predators are higher. In Central California, there is no significant difference in urchin abundances within protected areas as the current urchin predator, sea otters, are unilaterally protected. Therefore, we provide evidence that fully protected MPAs can be effective climate adaptation tools, but their ability to enhance resilience to extreme climate events depends upon region-specific environmental and ecological dynamics. As nations progress to protect 30% of the oceans by 2030 scientists and managers should consider whether protection will increase resilience to climate-change impacts given their local ecological contexts, and what additional measures may be needed.

ecology↗

bioRxiv2022

Towards transboundary networks of climate-smart marine reserves in the Southern California Bight

Climate-smart conservation addresses the vulnerability of biodiversity to climate change impacts but may require transboundary considerations. Here, we adapt and refine 16 biophysical guidelines for climate-smart marine reserves for the transboundary California Bight ecoregion. We link several climate-adaptation strategies (e.g., maintaining connectivity, representing climate refugia, and forecasting effectiveness of protection) by focusing on kelp forests and associated species. We quantify transboundary larval connectivity along [~]800 km of coast and find that the number of connections and the average density of larvae dispersing through the network under future climate scenarios could decrease by [~]50%, highlighting the need to protect critical steppingstone nodes. We also find that although focal species will generally recover with 30% protection, marine heatwaves could hinder subsequent recovery in the following 50 years, suggesting that protecting climate refugia and expanding the coverage of marine reserves is a priority. Together, these findings provide a first comprehensive framework for integrating climate resilience for networks of marine reserves and highlight the need for a coordinated approach in the California Bight ecoregion.

ecology↗

bioRxiv2020

Incorporating climate velocity into the design of climate-smart networks of protected areas

Climate change is redistributing terrestrial and marine biodiversity and altering fundamental ecological interactions. To adequately conserve biodiversity and promote its long-term persistence, protected areas should account for the ecological implications of species redistribution. Data paucity across many systems means that achieving this goal requires generic metrics that represent likely responses of multiple taxa to climate change. Climate velocity is one such metric, reflecting potential species range shifts at a generic level. Here, we explore four approaches to incorporating climate velocity metrics into the design of protected areas using the Mediterranean Sea as an illustrative example. Our methods are designed to meet two climate-smart planning objectives: 1) protect climate refugia by selecting slow-moving climate velocity areas, and 2) maintain the capacity of ecological systems to adapt by representing a suite of climate-velocity trajectory classes. We found that incorporating climate velocity as a cost measure in Marxan is the best approach for selecting slower-moving areas, which are good indicators of climate refugia. However, this approach fails to accommodate socio-economic cost data, and is probably impractical. Incorporating climate velocity as a boundary or as a feature provides both selection of slower-moving areas and solutions with lower socio-economic cost. Finally, we were able to design cost-effective networks of protected areas representing a suite of climate-velocity trajectories classes, which have the potential to help species adapt to a changing climate. This work presents simple and practical ways of including climate velocity in conservation plans on land and in the ocean to achieve the key climate-smart objectives of protecting climate refugia and enhancing ecological resilience.

ecology↗