Expansion of Butterfly Ranges

Why in News?

Recently, A global study published in Nature Ecology & Evolution assessed 1,758 butterfly species across 105 countries.

Key Findings

• Range Expansion – 80% species expanded into new territories; 79% shifted to cooler regions.
• Range Contraction – 27% species contracted ranges; 22% shifted along elevational gradients.
• Europe – Hotspot of range shifts; Sweden reported 61% expansions and 85% contractions.
• UK – Highest horizontal contraction (63%) and elevational shifts (18%).
• Mexico – Key hotspot for vertical shifts (39% species).

India’s Case – Tawny Coster

• Species – Tawny Coster (Acraea terpsicore), native to Indian subcontinent.
• Expansion – Rapidly spread across South Asia into Australia at 135 km per year.
• Comparison – Painted Lady shifted upslope in Mexico at 83 m/year and Queen butterfly downslope at 32 m/year.
• Significance – Example of “niche conservatism” – tracking suitable climates across vast distances.

Horizontal and Vertical Shifts

• Horizontal Expansions – Reported across all continents, including tropics (Brazil, Benin).
• Horizontal Contractions – Concentrated in temperate countries (Belgium, UK, Sweden).
• Elevational Shifts – Detected mainly in Northern Hemisphere; fewer records from tropics despite steeper lapse rates.
• Mountain Species – Two‑thirds of butterflies are mountain dwellers; highly vulnerable as mountain climates degrade.

Threats Identified

• Climate Change and Extreme Weather – Main driver of expansions and contractions.
• Human Intrusions and Disturbance – Linked to contractions in 143 species.
• Agriculture and Aquaculture – Major factor in range contractions.
• Other Threats – Residential/commercial development, invasive species, mining, energy production.
• Under‑representation – Amazon Basin, Southeast Asia, Central Africa lack adequate monitoring despite high diversity.

Conservation Implications

• Phenotypic Plasticity – Butterflies expand more than contract due to adaptive strategies.
• Micro‑refugia – Forested/shaded areas act as refuges during hot days.
• Adaptive Planning – Shift from static conservation to dynamic strategies.
• Paris Agreement Context – Limiting warming to 1.5–2°C crucial; mitigation must pair with adaptation.
• Measures – Protect micro‑refugia, buffer habitat edges, improve landscape connectivity.

Reference

Down To Earth | Wildlife-Biodiversity