Tracking submediterranean ecotone shifts under climate change scenarios using marcescent oaks as indicators – Nature

Report on the Projected Impact of Climate Change on the Submediterranean Ecotone and its Implications for Sustainable Development Goals

Executive Summary

This report analyzes the future geographic shifts of the submediterranean ecotone, a critical transitional zone between temperate and mediterranean climates, under various climate change scenarios. Using marcescent oaks as key indicators, the study models the ecotone’s response to changing climatic conditions. The findings confirm a significant northward expansion of the ecotone, overlapping with existing Eurosiberian forests. Conversely, a substantial loss of suitable habitat is projected for the southwestern Mediterranean, where viable areas will be restricted to higher altitudes and coastal refuges. These shifts have profound implications for achieving Sustainable Development Goal 13 (Climate Action) and Sustainable Development Goal 15 (Life on Land). The report underscores the urgent need for adaptive forest management and restoration strategies, informed by high-resolution modeling, to preserve biodiversity, maintain ecosystem services, and ensure the long-term resilience of these vital terrestrial ecosystems in the face of climate change and land-use pressures.

1.0 Introduction: Forest Ecosystems and the 2030 Agenda for Sustainable Development

Forests are fundamental to global sustainability, directly supporting the achievement of multiple Sustainable Development Goals (SDGs). They are critical repositories of terrestrial biodiversity and provide essential ecosystem services that underpin human well-being and climate stability.

• SDG 15 (Life on Land): Forests harbor the majority of the world’s biodiversity. Their conservation and restoration are central to halting biodiversity loss and promoting the sustainable use of terrestrial ecosystems.
• SDG 13 (Climate Action): As major carbon sinks, forests play an indispensable role in climate change mitigation. However, climate change itself threatens their health and resilience, potentially compromising their capacity to store carbon and regulate climate.

The submediterranean ecotone, a transitional zone in southern Europe and North Africa, is particularly sensitive to climatic shifts. This region, characterized by semi-deciduous and marcescent oak forests, is experiencing rapid changes that could undermine progress toward these SDGs. This report investigates the projected range shifts of this ecotone to inform conservation strategies that align with global sustainability targets.

1.1 The Submediterranean Ecotone: A Vulnerable Biogeographic Region

The submediterranean ecotone marks the transition between the temperate Eurosiberian and the arid Mediterranean biogeographic regions. It is characterized by unique semi-deciduous forests dominated by marcescent oaks (Quercus L.), which are adapted to both summer drought and winter frost. This ecotone is a hotspot of biodiversity, a common feature of transitional zones. However, its stability is threatened by accelerated climate change, which is projected to be particularly severe in the Mediterranean Basin, thereby jeopardizing the targets of SDG 15.

1.2 Research Objectives for Sustainable Forest Management

To address the challenges posed by climate change to this vital ecosystem, this study aims to provide data-driven insights for forest managers and policymakers. The objectives are to:

1. Predict the current and future distribution of the submediterranean ecotone under different climate scenarios.
2. Identify the key climatic drivers shaping its distribution.
3. Quantify the projected range shifts, identifying areas of habitat loss and gain.
4. Pinpoint regions highly susceptible to climate change to prioritize conservation and restoration efforts in line with SDG 13 and SDG 15.

2.0 Analysis of Ecotone Dynamics and Climatic Drivers

Species Distribution Models (SDMs) were developed using four marcescent oak species as proxies for the submediterranean ecotone: Quercus canariensis, Quercus faginea, Quercus pubescens, and Quercus pyrenaica. The ensemble model demonstrated excellent performance (TSS = 0.873, AUC = 0.985), ensuring robust projections.

2.1 Key Environmental Variables

The distribution of the submediterranean ecotone is primarily determined by bioclimatic factors, which are critical for understanding its vulnerability and informing climate adaptation strategies under SDG 13. The most significant variables were:

• Annual Precipitation (Bio12): The most influential factor, highlighting the ecotone’s dependence on adequate water availability.
• Temperature Seasonality (Bio04): Indicates a preference for climates with moderate temperature fluctuations.
• Minimum Temperature of the Coldest Month (Bio06): Defines the northern and altitudinal limits of the ecotone.

These factors underscore the ecotone’s reliance on a balanced climate, which is now being disrupted, threatening the stability required to maintain the biodiversity protected under SDG 15.

2.2 Current and Projected Geographic Shifts

The models reveal a dynamic future for the submediterranean ecotone, with significant consequences for regional biodiversity and ecosystem management.

Current Distribution

Under current conditions, the ecotone spans a large portion of Western Europe and North Africa. The highest richness of marcescent oak species is concentrated in the Iberian Peninsula, southern France, Italy, and coastal North Africa, marking these as core areas for biodiversity conservation (SDG 15).

Future Projections (2041–2100)

Future climate scenarios project a decisive geographic shift:

• Northward and Eastward Expansion: The ecotone is expected to gain suitable habitat in northern and eastern Europe, potentially reaching Scandinavia. This shift presents an opportunity for managed ecosystem transition but also risks disrupting existing temperate forests.
• Southern Contraction: Significant habitat loss is predicted for inland North Africa and southern Iberia. Suitable conditions will become fragmented, persisting primarily in coastal zones and at higher altitudes. These areas will become critical climate refugia, essential for preserving genetic diversity and preventing species extinction, a key target of SDG 15.

Overall, while 60–80% of the current suitable area is projected to remain stable, the gains in the north are expected to exceed the substantial losses in the south. This net change highlights a large-scale reorganization of European forest landscapes, demanding a coordinated, transnational response to meet conservation goals.

3.0 Discussion: Implications for SDG 13 (Climate Action) and SDG 15 (Life on Land)

The projected shifts of the submediterranean ecotone present both challenges and opportunities for achieving the 2030 Agenda. The findings confirm that climate change is actively reshaping terrestrial ecosystems, necessitating a paradigm shift in forest management from preservation to proactive adaptation.

3.1 Threats to SDG 15 in Southern Regions

The contraction of the ecotone in the south poses a direct threat to SDG 15 (Life on Land). The loss of marcescent oak forests will lead to:

• Biodiversity Loss: Fragmentation of habitats will isolate populations, increasing extinction risk for endemic species and those with limited dispersal ability, such as Quercus canariensis.
• Ecosystem Degradation: The transition to more drought-tolerant, evergreen sclerophyll woodlands could alter soil composition, water cycles, and fire regimes, leading to a decline in essential ecosystem services.
• Desertification: The loss of forest cover in these vulnerable regions could accelerate land degradation, directly contravening target SDG 15.3 (combat desertification).

Protecting the identified coastal and mountain refugia is therefore paramount for safeguarding the unique biodiversity of this region.

3.2 Opportunities and Challenges for SDG 13 and SDG 15 in Northern Regions

The northward expansion of the ecotone into temperate zones creates a new ecological dynamic. Marcescent oaks may act as a buffer against the decline of temperate species like beech and pedunculate oak, which are less resilient to increasing drought.

• Enhancing Climate Resilience (SDG 13): The introduction of more drought-tolerant marcescent species could help maintain forest cover and productivity in areas where traditional temperate forests are projected to decline. This contributes to the resilience of ecosystems and their capacity for carbon sequestration.
• Managing Ecosystem Transition (SDG 15): This expansion will lead to novel ecosystems, creating a turnover in species composition. Management strategies must facilitate this transition to avoid ecological disruption and maximize biodiversity benefits. This includes considering assisted migration for species unable to disperse naturally.

4.0 Conclusion and Recommendations for Sustainable Forest Management

This study confirms that the submediterranean ecotone is undergoing a rapid, climate-driven transformation. Its northward expansion and southern contraction will significantly alter the landscape of European forests. To address these changes and align with the Sustainable Development Goals, adaptive and forward-looking strategies are essential.

4.1 Recommendations

1. Implement Adaptive Forest Management: Management plans must move beyond static conservation and incorporate climate change projections. This includes enhancing species and genetic diversity to bolster forest resilience against drought and other climate-related hazards, directly supporting SDG 13.1 and SDG 15.2.
2. Prioritize Conservation of Climate Refugia: The identified southern refugia (coastal and high-altitude areas) must be prioritized for conservation to protect vulnerable populations and genetic diversity, a critical action for SDG 15.5 (take urgent action to halt the loss of biodiversity).
3. Support Assisted Migration and Ecosystem Restoration: In transition zones, strategies like assisted migration should be explored to introduce drought-resistant species and provenances. This approach can help maintain forest ecosystem services and support initiatives like the European Commission’s Nature Restoration Law.
4. Invest in High-Resolution Modeling: Further research using finer-scale models is needed to better understand the role of local topography and soil conditions. This will enable more precise planning for conservation and restoration actions, ensuring that efforts to achieve SDG 13 and SDG 15 are effective and resource-efficient.

By integrating these scientific insights into policy and practice, stakeholders can better navigate the challenges of climate change, ensuring that Europe’s forests continue to support biodiversity, regulate climate, and provide for human well-being for generations to come.

Analysis of Sustainable Development Goals in the Article

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

• SDG 13: Climate Action

  The article is fundamentally centered on the impacts of climate change. It explicitly investigates how “future range shifts of the submediterranean ecotone caused by climate change” will affect marcescent oak forests. The study uses various climate change scenarios (SSP370 and SSP585) to project these impacts, addressing the urgent need to combat climate change and its effects on natural ecosystems. The text mentions “the rapid pace of modern climate change,” “rising temperatures,” and “decrease in precipitation,” directly linking the research to the core concerns of SDG 13.

• SDG 15: Life on Land

  This goal is directly addressed as the article focuses on protecting, restoring, and promoting the sustainable use of terrestrial ecosystems, specifically forests. It highlights that “Forests harbor most of the world’s biodiversity” and are threatened by “loss, degradation, and fragmentation.” The research aims to provide critical information for “forest conservation and restoration,” “adaptive forest management,” and preserving biodiversity within the submediterranean ecotone, which is described as a “reservoir for unique and endemic species.”

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

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

  The article contributes to this target by providing “spatially explicit projections about the future climatic suitability of species and communities.” This information is crucial for developing “adaptive forest management and restoration” strategies to help these ecosystems withstand future climate conditions. The identification of future “refuges and expansion zones” is a direct input for strengthening the resilience of these forests.

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

  The research is intended to “inform forest managers and anticipate conservation actions” and “alert policy makers.” By projecting the future distribution of the submediterranean ecotone, the study provides scientific evidence that can be integrated into regional and national conservation planning and land management policies, such as the “European Commission’s Nature Restoration Law proposal” mentioned in the conclusion.

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

  The article’s primary objective is to support the conservation and restoration of submediterranean forests. It quantifies the current and future suitable habitat for these forests, identifying areas of loss and gain. The discussion emphasizes the need to “preserve these forests” and their associated ecosystem services, such as “carbon storage, soil formation and conservation.”

• 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 article directly calls for “effective measures and governance to mitigate widespread threats” to forests and advocates for “adaptive forest management and restoration.” The findings are presented as a tool to “plan management and restoration strategies within a context of high disturbance by land use,” which aligns with promoting sustainable forest management and restoring degraded forest areas.

• 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 study addresses this target by identifying areas where submediterranean forests, which have “high biodiversity,” are under threat. It specifically mentions that some species, like *Quercus canariensis*, are “prone to be dramatically affected by global warming” and have a “Data Deficient and unknown IUCN status.” The research aims to provide information crucial for planning conservation strategies to prevent habitat degradation and protect these species.

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

• Indicator for Target 15.1 (related to Indicator 15.1.1: Forest area as a proportion of total land area):

  The article provides quantitative measurements of the forest ecotone’s area and its projected changes. It states that “60–80% (from 20,860 km² to 22,327 km²) of the current submediterranean area will remain suitable,” and quantifies “total losses range from 3.5% (1127 km²) to 11.9% (3885 km²).” These figures on habitat gain, loss, and stability serve as a direct indicator of the changing extent of this forest ecosystem.

• Indicator for Target 13.1 (Resilience and Adaptation):

  The projected “range shifts” of the ecotone (northward expansion and southern contraction) under different climate scenarios (SSP370 and SSP585) act as an indicator of the ecosystem’s response and vulnerability to climate change. The identification of “altitudinal refugia” and stable coastal zones indicates areas with higher resilience that can be prioritized for conservation.

• Indicator for Target 15.5 (Biodiversity and Threatened Species):

  The article implies several biodiversity indicators. Firstly, it uses “species richness (number of species) of marcescent oak species” to map biodiversity hotspots within the ecotone. Secondly, it explicitly references the IUCN Red List, an established system for tracking threatened species, by noting the “Data Deficient and unknown IUCN status” of *Q. canariensis*. This directly relates to Indicator 15.5.1 (Red List Index).

• Indicator for Climate Change Impacts (related to Target 13.1):

  The study uses specific bioclimatic variables as indicators of the environmental drivers of change. The results identify “annual precipitation (Bio12),” “temperature seasonality (Bio04),” and “minimum temperature of the coldest month (Bio06)” as the primary determinants of the oak forests’ distribution. Tracking changes in these climatic indicators is essential for monitoring progress in adapting to climate change.

4. Table of SDGs, Targets, and Indicators

Source: nature.com