Conversion of abandoned paddy fields to productive land through mangrove restoration in Myanmar’s Ayeyarwady Delta

Abstract

In Myanmar’s Ayeyarwady Delta, mangrove forests were widely converted to paddy fields, then abandoned. However, the mangrove ecosystems often fail to recover. To identify the mangrove restoration options in these fields, we conducted the current study in Pyindaye Forest Reserve, Pyapon Township of the Delta by examining the structural and functional responses to restoration for two common mangrove species (Avicennia officinalis and Bruguiera sexangula) after three post-abandonment periods (4, 8, and > 10 years), the natural recovery after these periods, and management to improve degraded forests dominated by the two species. Without replanting, we observed no mangrove cover or regeneration more than 10 years after abandonment. The sites were dominated by a perennial grass (Paspalum vaginatum), sparse climber, herbs, and spiny shrubs. With increasing the abandoned period, we observed decreasing soil quality and increasing vegetation cover by the grass, herbs, and spiny shrubs in response to increasingly harsh micro-environmental conditions for natural recovery of mangrove. Without human assistance, the abandoned paddy fields will not recover their productivity after more than 10 years. However, with increasing the period of establishing mangrove plantations in the abandoned fields, the ecosystem showed improved vegetation structure and regeneration of both planted and non-planted species. The soil conditions improved during mangrove recovery, and a well-developed canopy and aerial root system developed. By 8 years after mangrove establishment, the land could be used again as paddy fields due to suppression of P. vaginatum and the improved micro-environment. The managed forests showed the best structural attributes, conditions for regeneration, and micro-environmental conditions for plant growth and regeneration. Our results suggest three options for managing the abandoned paddy fields: paddy cultivation based on fallow periods with mangrove establishment, mangrove planting for wood production, and mangrove planting for environmental restoration.