Global Mapping of Arbuscular Mycorrhizal Fungi

Context:

A recent study published in the journal ‘Science’ has produced the first global map of Arbuscular Mycorrhizal (AM) fungi, uncovering the immense scale of underground fungal networks that support plant life and contribute significantly to climate regulation.

Key Findings of the Study:

• • • Global topsoils contain approximately 110 quadrillion km of fungal hyphae, equivalent to nearly a billion trips between the Earth and the Sun.
    • AM fungal networks store around 300 million tonnes of carbon.
    • These fungi help sequester nearly 4 billion tonnes of CO₂-equivalent annually, representing about 11% of global human-induced carbon emissions.
    • Nearly 40% of global AM fungal networks are concentrated in grassland ecosystems, including:
      • South Sudan grasslands
      • Tibetan Plateau
      • India's Banni Grasslands in Gujarat
    • Croplands exhibit around 50% lower fungal density compared to natural ecosystems.

What are Arbuscular Mycorrhizal (AM) Fungi?

AM fungi are ancient soil microorganisms that form mutually beneficial symbiotic relationships with nearly 80% of terrestrial plant species.

How does the Symbiosis Work?

Fungi provide:

• • • Phosphorus, nitrogen, zinc, and water from the soil.
    • Enhanced nutrient absorption through extensive underground networks.

Plants provide:

• • • Sugars and carbon compounds produced through photosynthesis.

This nutrient exchange improves plant growth and ecosystem productivity.

Important Structures:

Arbuscules

• • • Tree-like structures formed inside root cells.
    • Main sites of nutrient exchange.

Vesicles

• • • Storage organs containing lipids and nutrients.

Hyphae

• • • Thread-like filaments forming extensive underground networks connecting plants and soil.

Ecological and Agricultural Significance:

Climate Change Mitigation

• • • Significant carbon sequestration capacity.
    • Supports soil carbon storage and reduces atmospheric CO₂ levels.

Soil Health

• • • Produces glomalin, a glycoprotein that improves soil structure and reduces erosion.

Sustainable Agriculture

• • • Enhances nutrient-use efficiency.
    • Improves drought tolerance and resistance to salinity.
    • Reduces dependence on chemical fertilizers.

Biodiversity Conservation

• • • Supports ecosystem resilience and plant diversity.

Threats to AM Fungi:

The study warns that AM fungal networks are increasingly threatened by:

• • • Conversion of grasslands into croplands.
    • Intensive tillage practices.
    • Excessive use of chemical fertilizers.
    • Monoculture farming systems.
    • Land degradation and habitat loss.

Grasslands are currently being converted to agriculture at a rate nearly four times faster than forests, posing a major risk to these underground ecosystems.

Significance for India:

India's Banni Grasslands have been identified as a global hotspot for AM fungal diversity. The findings support India's efforts towards:

• • • Natural Farming
    • Sustainable agriculture
    • Land restoration
    • Climate change mitigation
    • Soil health management

Conclusion:

The global mapping of AM fungi reveals that Earth's underground fungal networks function as critical ecological infrastructure supporting food security, biodiversity, and climate regulation. Recognizing and conserving these hidden ecosystems is essential for achieving sustainable agriculture and global climate goals.