Microclimates slow and alter the direction of climate velocities in tropical forests – Nature

Report on Microclimate Velocity and its Implications for Sustainable Development Goals

Executive Summary

This report analyzes the critical role of forest microclimates in mitigating the impacts of climate change on biodiversity, directly addressing Sustainable Development Goal 13 (Climate Action) and SDG 15 (Life on Land). Research based on mechanistic microclimate models reveals that vegetation structure significantly reduces the speed and alters the direction of “climate velocity”—the rate at which species must migrate to track survivable climate conditions. Structurally complex forests create localized thermal refuges, or microrefugia, which enhance species’ resilience by reducing the need for large-scale migration. These findings underscore the necessity of integrating fine-scale habitat data into conservation strategies and highlight that the protection and restoration of complex forest ecosystems are fundamental actions for achieving global sustainability targets.

Analysis of Findings in the Context of SDG 13 (Climate Action)

The study provides critical evidence for natural adaptation mechanisms that strengthen resilience to climate-related hazards. By quantifying how forest structure buffers temperature extremes, the research informs strategies for climate change adaptation (SDG Target 13.1).

Key Findings on Climate Velocity Reduction

• Reduced Magnitude: Microclimate heterogeneity created by dense vegetation and complex topography dramatically slows the speed of climate velocity. For organisms living in the forest understory, the velocity of maximum temperature change was halved compared to standard “free-air” models.
• Vertical Refugia: For canopy-dwelling organisms, the velocity was nearly zero, with the necessary movement being vertically downward into cooler, more shaded parts of the canopy rather than across the landscape.
• Mechanism: This reduction is not due to a slower rate of overall warming but to a significant increase in the spatial gradient of temperature. In essence, vegetation creates a diverse mosaic of temperatures over short distances, meaning organisms can find cooler conditions by moving meters instead of kilometers.

Implications for SDG 15 (Life on Land)

The findings directly support the urgent action needed to halt biodiversity loss and protect terrestrial ecosystems. The role of forests as microrefugia is a key, yet often overlooked, ecosystem service essential for achieving SDG 15 targets.

The Role of Forest Structure in Biodiversity Conservation

1. Protecting Biodiversity (SDG 15.5): By providing thermal refuges, structurally complex forests allow species to persist locally in the face of warming, reducing the risk of extirpation. This is especially critical for species with limited dispersal capabilities and those in regions with otherwise homogeneous macroclimates, such as tropical lowlands.
2. Altering Migration Patterns: The direction of climate velocity is altered by vegetation. Instead of moving predictably upslope, species may find refuge by moving towards areas of denser vegetation. This challenges traditional conservation models and highlights the need for a more nuanced understanding of species’ responses to climate change.
3. Sustainable Forest Management (SDG 15.2): The study demonstrates that the value of a forest in climate adaptation is tied to its three-dimensional structural complexity. This implies that sustainable management must go beyond merely maintaining forest cover to actively preserving and restoring this complexity through practices that avoid homogenization of the canopy.

Threats and Vulnerabilities

• Deforestation and Degradation: The climate-buffering capacity described is contingent on the health and integrity of the forest. Deforestation, logging, and degradation from climate-related disturbances (droughts, fires) reduce canopy cover and structural complexity.
• Increased Vulnerability: The loss of this buffering effect would accelerate microclimate velocities, homogenize local temperatures, and eliminate microrefugia, thereby increasing the vulnerability of forest understory communities and undermining progress towards SDG 15.

Recommendations for Policy and Conservation

Integrating Microclimate Science into Sustainability Strategies

To effectively advance SDG 13 and SDG 15, conservation and climate adaptation policies must evolve to incorporate the dynamics of microclimates.

1. Refine Conservation Planning: Move beyond coarse-resolution climate models and incorporate fine-scale data on vegetation structure and topography to identify and prioritize areas that can serve as climate refugia.
2. Promote Structurally Complex Forests: Conservation and restoration efforts must explicitly target the creation and maintenance of structural complexity. This includes promoting multi-layered canopies and diverse vegetation densities to maximize the formation of microclimates.
3. Enhance Monitoring and Research: Support the use of technologies like LiDAR to monitor forest structure over time. This data is essential for understanding how forest degradation impacts buffering capacity and for developing adaptive management strategies that enhance ecosystem resilience.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

1. SDG 13: Climate Action

   The article is fundamentally about the impacts of climate change on ecosystems. It directly addresses the concept of “climate velocity,” which it defines as “the speed and direction species must move to track climate change.” The entire study is framed around understanding how species and ecosystems respond to global warming, which is the central theme of SDG 13.

2. SDG 15: Life on Land

   The research focuses on terrestrial ecosystems, specifically tropical montane forests, and the biodiversity within them. It explores how forest structure (vegetation complexity) can mitigate the effects of climate change on species, thereby protecting biodiversity. The article discusses the importance of conserving and restoring forests, the threat of deforestation, and the need to halt the degradation of natural habitats, all of which are core components of SDG 15.

2. What specific targets under those SDGs can be identified based on the article’s content?

1. SDG 13: Climate Action

   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.

     The article investigates how structurally complex forests create “localized microrefugia, enabling short-term persistence of species under warming conditions.” This directly relates to building ecosystem resilience and enhancing the adaptive capacity of species to the hazard of rising temperatures. The study demonstrates that vegetation provides a natural mechanism for adaptation.

   • Target 13.2: Integrate climate change measures into national policies, strategies and planning.

     The findings have direct implications for conservation planning. The article states that its findings “emphasize the need to integrate fine-scale habitat heterogeneity into predictions of climate resilience.” This suggests that conservation strategies and policies must account for microclimates to be effective, thereby integrating climate change measures into planning.

2. SDG 15: Life on Land

   • Target 15.1: By 2020, ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, mountains and drylands, in line with obligations under international agreements.

     The article’s conclusion that “Maintaining and restoring structurally complex forests will therefore be critical to reduce microclimate velocities and provide microclimatic refugia” is a direct call for the conservation and restoration of forest ecosystems to preserve their climate-buffering services.

   • Target 15.2: By 2020, promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests and substantially increase afforestation and reforestation globally.

     The research highlights the negative impacts of forest degradation, noting that “Deforestation combined with tree mortality… are reducing canopy cover globally,” which can “homogenizing microclimate variability.” This underscores the urgency of halting deforestation and restoring forests to maintain their structural complexity and ecological functions.

   • Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity and, by 2020, protect and prevent the extinction of threatened species.

     The entire study revolves around understanding species’ response to climate change to prevent biodiversity loss. By showing that microclimates can slow the required pace of migration, the article identifies a key mechanism for species persistence. It states that dense forest patches “may increase short-term persistence in the landscape,” which is crucial for protecting threatened species from extinction due to climate change.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

The article does not explicitly name official SDG indicators, but it uses and discusses several metrics that can serve as direct or proxy indicators for measuring progress.

• Climate Velocity (m yr⁻¹)

  This is the central metric of the study, calculated as “the temporal rate of climate change divided by the spatial gradient of climate change.” It measures the rate at which species must migrate to stay within their thermal niche. The article shows that microclimate heterogeneity reduces this velocity. It can be used as an indicator of ecosystem vulnerability (higher velocity) or resilience (lower velocity) to climate change, relevant to Targets 13.1 and 15.5.

• Vegetation Structure and Density (e.g., Plant Area Index – PAI)

  The study uses LiDAR data to map vegetation structure, including PAI, which it defines as “(m² per m²).” It demonstrates that “maximum temperature velocities were often directed towards denser vegetation.” PAI and other measures of forest structural complexity can serve as indicators for the quality of forest ecosystems and their capacity to provide climate refugia, aligning with Targets 15.1 and 15.2.

• Canopy Cover

  The article explicitly mentions the global reduction in “canopy cover” due to deforestation and tree mortality. The extent and density of canopy cover is a direct indicator of forest health and its ability to buffer microclimates. This aligns with official SDG indicator 15.1.1 (Forest area as a proportion of total land area) and 15.2.1 (Progress towards sustainable forest management).

• Rate of Temperature Change (°C yr⁻¹)

  This is a component of the climate velocity calculation and is a direct measure of the local impact of climate change. The article analyzes this metric to understand its contribution to climate velocity, finding that understories are experiencing warming rates similar to free-air conditions. This serves as a fundamental indicator for monitoring climate change impacts under SDG 13.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com