Report on Predicting Potentially Suitable Bletilla striata Habitats in China under Future Climate Change Scenarios Using the Optimized MaxEnt Model

Abstract

Bletilla striata, a valuable traditional Chinese medicinal and ornamental plant, faces challenges in cultivation due to unscientific habitat selection causing low yields and poor quality. Utilizing the optimized MaxEnt model, this study analyzed the influence of environmental factors on B. striata distribution and projected habitat changes under four climate change scenarios (SSP1.26, SSP2.45, SSP3.70, SSP5.85) over three time periods (current, 2050s, 2070s). The model demonstrated high accuracy with solar radiation, annual temperature range, and mean diurnal range identified as dominant factors. Current suitable habitats cover approximately 3.007 million km² in southern China, but future climate change predicts significant habitat reduction and northward centroid shifts. These findings support sustainable development goals (SDGs) related to life on land (SDG 15), climate action (SDG 13), and responsible production (SDG 12).

Introduction

Bletilla striata thrives in diverse habitats across southern China and is renowned for its medicinal properties including hemostasis, swelling reduction, and wound healing. Its polysaccharides have pharmacological benefits, and its gum is utilized in medical and cosmetic industries. The increasing industrial demand has led to rapid cultivation expansion but also highlighted disparities in yield and quality due to inadequate habitat suitability research.

Climate change, characterized by rising temperatures and water scarcity, adversely affects plant growth and productivity, including B. striata. Understanding species distribution in response to environmental variables is crucial for conservation and sustainable use, aligning with SDG 15 (Life on Land) and SDG 13 (Climate Action).

Species Distribution Models (SDMs), particularly the MaxEnt model, are effective tools for predicting species habitats using presence-only data. The optimized MaxEnt model enhances prediction accuracy and ecological relevance, supporting informed conservation strategies.

Materials and Methods

1. Data Collection and Processing

1. Distribution Data: 269 georeferenced occurrence records of B. striata were compiled from global and Chinese biodiversity databases, ensuring spatial independence by thinning data points within 5 km.
2. Environmental Variables: Initially, 24 bioclimatic and topographic variables were considered, sourced from WorldClim, National Tibetan Plateau Data Center, and digital elevation models.
3. Variable Selection: Using Jackknife tests and correlation analyses, 15 key environmental factors with significant contributions and low multicollinearity were selected for modeling.

2. MaxEnt Model Optimization and Evaluation

• Model parameters were optimized using the “kuenm” R package, testing combinations of regularization multipliers and feature classes to minimize overfitting.
• Model performance was assessed via the Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC), with an AUC of 0.89 indicating good predictive accuracy.
• Habitat suitability was classified into four categories based on threshold values: not suitable, low, medium, and high suitability.

3. Future Habitat Projection and Analysis

• Future climate scenarios (SSP1.26, SSP2.45, SSP3.70, SSP5.85) for 2050 and 2070 were incorporated to predict changes in habitat suitability.
• Spatial analyses identified areas of habitat expansion, contraction, and centroid shifts using ArcGIS SDM toolkit.

Results and Analysis

1. Model Performance

The optimized MaxEnt model achieved a statistically significant fit (p-value = 0) with minimal omission error (0.0333%) and an AUC of 0.89, confirming its reliability for predicting B. striata distribution.

2. Current Suitable Habitat Distribution

Potential suitable habitats predominantly occur in Southwest and South China, including Guizhou, Chongqing, Sichuan, Yunnan, Hubei, Hunan, and Guangxi provinces. The total suitable area is approximately 300,700 km², with high suitability areas constituting 31.33%.

3. Key Environmental Factors Influencing Distribution

1. Solar Radiation (SRAD): 45.5% contribution
2. Annual Temperature Range (bio7): 39.4% contribution
3. Mean Diurnal Temperature Range (bio2): 3.4% contribution
4. Vapor Pressure (VAPR): 3.3% contribution

Temperature-related variables had a higher influence (61.7%) compared to precipitation variables (19.5%). Thresholds for dominant factors were identified to guide habitat suitability assessments.

4. Future Habitat Changes under Climate Scenarios

• All scenarios predict significant reductions in highly suitable habitats, exceeding 60% decline by 2070.
• The SSP5.85 scenario (conventional development path) showed the most severe habitat loss, highlighting the impact of high temperatures.
• Centroid of suitable habitats shifts northward over time, indicating potential range shifts due to climate change.

Discussion

1. Model Predictive Performance and Implications for SDGs

The study’s robust MaxEnt model provides critical insights into B. striata habitat suitability, supporting SDG 15 by informing conservation efforts and SDG 13 by addressing climate change impacts on biodiversity. Despite limitations such as exclusion of biological and soil factors, the model serves as a valuable tool for ecosystem management and sustainable resource use (SDG 12).

2. Ecological Characteristics and Distribution

The findings align with previous research, confirming southern China as the core distribution area. Solar radiation and temperature variability are key determinants, emphasizing the need to consider these factors in cultivation and conservation planning.

3. Impact of Climate Change on B. striata

• Rising temperatures and altered light conditions negatively affect growth and physiological processes.
• Heat stress and drought reduce photosynthetic efficiency and increase vulnerability to pests and diseases.
• Habitat contraction and fragmentation threaten species survival, underscoring the urgency for adaptive management strategies.

4. Habitat Selection and Conservation Strategies

1. Strengthen Nature Reserves: Expand and establish reserves to protect wild populations and biodiversity hotspots, contributing to SDG 15.
2. Enhance Germplasm Research: Focus on breeding and genetic resource conservation to improve resilience and sustainable cultivation.
3. Promote Sustainable Cultivation: Develop planting bases in suitable habitats with interventions such as shading and intercropping to mitigate climate stress.

Conclusion

Climate change poses significant threats to B. striata habitats in China, with projected reductions in suitable areas and northward shifts in distribution centroids. Solar radiation and temperature variability are critical environmental drivers. To align with Sustainable Development Goals, particularly SDG 13 (Climate Action), SDG 15 (Life on Land), and SDG 12 (Responsible Consumption and Production), it is imperative to implement conservation measures, enhance breeding programs, and promote sustainable cultivation practices to ensure the long-term viability of B. striata resources.

1. Sustainable Development Goals (SDGs) Addressed or Connected

1. SDG 13: Climate Action
   • The article discusses the impact of climate change on the distribution and habitat suitability of Bletilla striata, highlighting the need for climate adaptation strategies.
2. SDG 15: Life on Land
   • Focus on conservation and sustainable use of terrestrial ecosystems, protection of endangered species, and habitat preservation for B. striata.
3. SDG 3: Good Health and Well-being
   • B. striata is an important traditional Chinese medicine resource with medicinal properties, contributing to health and well-being.
4. SDG 12: Responsible Consumption and Production
   • Emphasis on sustainable cultivation and resource management of B. striata to meet increasing demand without depleting wild populations.

2. Specific Targets Under Identified SDGs

1. SDG 13: Climate Action
   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters.
   • Target 13.3: Improve education, awareness-raising and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning.
2. SDG 15: Life on Land
   • Target 15.1: Ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services.
   • Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity, and protect endangered species.
3. SDG 3: Good Health and Well-being
   • Target 3.8: Achieve universal health coverage, including access to safe, effective, quality, and affordable essential medicines and vaccines.
4. SDG 12: Responsible Consumption and Production
   • Target 12.2: Achieve the sustainable management and efficient use of natural resources.
   • Target 12.5: Substantially reduce waste generation through prevention, reduction, recycling, and reuse.

3. Indicators Mentioned or Implied to Measure Progress

1. Indicators Related to SDG 13 (Climate Action)
   • Changes in the area and suitability of B. striata habitats under different climate scenarios (e.g., SSP1.26, SSP2.45, SSP3.70, SSP5.85).
   • Shift in the centroid of suitable habitats northward as a measure of species adaptation or migration due to climate change.
2. Indicators Related to SDG 15 (Life on Land)
   • Area of suitable habitat classified into fitness grades: not suitable, low, medium, and high suitability areas (measured in km²).
   • Contribution rates of environmental factors (solar radiation, annual temperature range, mean diurnal range, vapor pressure) affecting species distribution.
   • Population status and conservation status of B. striata (listed in Appendix I of CITES and national protection lists).
3. Indicators Related to SDG 3 (Good Health and Well-being)
   • Availability and quality of B. striata as a medicinal resource, indirectly measured by yield and quality variations due to habitat suitability.
4. Indicators Related to SDG 12 (Responsible Consumption and Production)
   • Extent of cultivated area and sustainable management practices for B. striata cultivation.
   • Reduction in habitat loss and degradation through conservation measures.

4. Table of SDGs, Targets, and Indicators

Source: nature.com