<p>The importance of the land sector in addressing the climate and nature crises has gained worldwide attention. Nature-based solutions were a key topic at the recent United Nations Conference of the Parties (COP26) in Glasgow to limit global warming to well below 2 degrees. The conservation, restoration, and improved management of peatlands play a significant role in Indonesia's nature-based solutions.</p><p>The eddy covariance measurements of net ecosystem carbon dioxide and methane exchanges from a coastal peatland in Sumatra, Indonesia indicate that the GHG balance increased from 20.0 ± 4.5 tCO<sub>2</sub>e ha<sup>−1</sup> yr<sup>−1</sup> at the intact site (undrained and undisturbed forest cover) to 43.8 ± 1.5 tCO<sub>2</sub>e ha<sup>−1</sup> yr<sup>−1</sup> at the degraded site (drained with canal system and selectively logged). The significant carbon dioxide emissions from the intact site, during an extreme drought caused by a positive Indian Ocean Dipole phase combined with El Niño event, highlight the potential importance of climate regime in determining the GHG budget of tropical peatlands.</p><p>Although the measurements indicate that both intact and degraded peatlands in this study are warming the atmosphere, it remains clear that protection of the remaining intact tropical peatlands offers a viable way to avoid substantial GHG emissions from this globally important ecosystem, which for our study in Sumatra was 24 ± 5 tCO<sub>2</sub>e ha<sup>−1</sup> yr<sup>−1</sup>. These results highlight that protecting all remaining intact peat swamp forests in Indonesia (6.2 Mha) from degradation will avoid GHG emissions of around 0.15 GtCO<sub>2</sub>e yr<sup>-1</sup>, this equates to ~10% of Indonesia’s GHG emissions in 2016.</p><p>Additionally, tropical peatland conservation contributes directly to the UN Sustainable Development Goals by fostering unique biodiversity and ecosystem services.</p>

<p>Tropical peatlands play an important role in addressing the climate and nature functions. In these ecosystems, hydrology strongly controls their geomorphology, ecology, and carbon cycle. More frequent and severe droughts driven by climate extremes (e.g. El Niño Southern Oscillation and the Indian Ocean Dipole events) may alter their local hydrology. In addition, growing dependencies on tropical peatlands due to population growth and economic development has resulted in land-cover change. Alteration in the hydrological processes under changing climate and land-cover may have crucial implications on tropical peatlands, but such impacts remain poorly understood.</p><p>In this context, we used a coupled MIKE SHE and MIKE Hydro River model to represent the hydrological processes within Pulau Padang (~1,100 km<sup>2</sup>), a peat-dominated island in the eastern coast of Sumatra, Indonesia. The island is a mosaic landscape of peat swamp forest, smallholder area, and industrial plantation. We collected a comprehensive vegetation and peat properties data from field measurements, supported by high-resolution digital terrain model derived from airborne LiDAR, for the model setup. We calibrated and validated the model against observed groundwater level and stream flow data distributed across the island. Finally, we also evaluated the impacts of land-cover change trajectory in the island by comparing the water balance components (i.e. evapotranspiration, runoff, and storage change) for different hydroclimatic extremes (i.e. El Niño and La Nina) under its current condition (baseline year of 2016) to that of its past (25-year look back period) and future (50-year trajectory) conditions.</p><p>This research should contribute to advance the understanding of the landscape scale hydrological processes in tropical peatlands under land-cover change trajectory, which are important to provide scientific basis for stakeholders involved in guiding responsible peatland management practices. This presentation will discuss the modeling approach and preliminary results.</p>