Abstract. Drained peatlands are one of the main sources of carbon dioxide (CO2) emissions globally. Emission reduction and, more generally, ecosystem restoration can be enhanced by raising the water table using canal or drain blocks. When restoring large areas, the number of blocks becomes limited by the available resources, which raises the following question: in which exact positions should a given number of blocks be placed in order to maximize the water table rise throughout the area? There is neither a simple nor an analytic answer. The water table response is a complex phenomenon that depends on several factors, such as the topology of the canal network, site topography, peat hydraulic properties, vegetation characteristics and meteorological conditions. We developed a new method to position the canal blocks based on the combination of a hydrological model and heuristic optimization algorithms. We simulated 3 d dry downs from a water saturated initial state for different block positions using the Boussinesq equation, and the block configurations maximizing water table rise were searched for by means of genetic algorithm and simulated annealing. We applied this approach to a large drained peatland area (931 km2) in Sumatra, Indonesia. Our solution consistently outperformed traditional block locating methods, indicating that drained peatland restoration can be made more effective at the same cost by selecting the positions of the blocks using the presented scheme.

In the Lower Mekong River Basin (LMB), deforestation rates are some of the highest in the world as land is converted primarily into intensive agriculture and plantations. While this has been a key for the region’s economic development, rural populations dependent on the freshwater water resources that support their fishing and agriculture industries are increasingly vulnerable to the impacts of flood, drought and non-point source pollution. Impacts of deforestation on ecosystem services (ES) including hydrological ES that control the availability and quality of fresh water across the landscape, regulating floods and droughts, soil erosion and non-point source pollution are known. Despite this understanding at the hillslope level, few studies have been able to quantify the impact of wide-scale deforestation on larger tropical watersheds. This study introduces a new methodology to quantify the impact of deforestation on water-based ES in the LMB with a focus on Cambodia by combining spatial datasets on forest loss from remote sensing and spatially-explicit hydrological modeling. Numerous global and regional remote sensing products are synthesized to develop detailed land use change maps for 2001 to 2013 for the LMB, which are then used as inputs into a hydrological model to develop unique spatial datasets that map ES changes due to deforestation across the LMB. The results point to a clear correlation between forest loss and surface runoff, with a weaker but upward trending relationship between forest loss and sediment yield. This resulted in increased river discharge for 17 of the 22 watersheds, and increased sediment for all 22 watersheds. While there is considerable variability between watersheds, these results could be helpful for prioritizing interventions to decrease deforestation by highlighting which areas have experienced the greatest change in water-based ES provision. These results are also presented in a web-based platform called the Watershed Ecosystem Service Tool.

Drainage canals have triggered peat subsidence and lowered groundwater table, enabling wildfires and peat degradation in Riau, Indonesia. This study examines the changes on groundwater table, peat subsidence rate, and carbon emission in response to deforestation and land cover changes. We established 31 study sites in some land cover types (i.e., oil palm plantation, acacia regrowth and shrub), with 124 monitoring shallow wells and 31 subsidence poles that were setup and have been monitored for 18 months. Groundwater table of all plots averaged -55 cm in Dosan Village, higher than that in Dayun Village (-66 cm). In accordance, peat had subsided in faster rate (8.4 cm year−1) in Dayun Village than that in Dosan (3.3 cm year−1). This average annual groundwater table has resulted in carbon emissions from peat decomposition up to 66 t CO2eq ha−1 year−1. On the other hand, canal discharge of these sites ranged from 2 to 73 dm3 s−1, averaging 26 dm3 s−1. These results evidence that land uses converted from peat forest, and the dimension of canal control the decrease in groundwater table, the pace of peat subsidence, and rate of carbon emissions in tropical peatlands.

Considerable expansion of red deer farming has occurred in the South Island high country of New Zealand. On these farms, breeding hinds are usually continuously grazed (set-stocked) at low population densities in large highly modified native-tussock grassland paddocks during their calving and lactation seasons. The present study determined how these hinds use the tussock grassland over this critical period, identifying the most essential resources for them and also some potential long-term consequences of their behaviour on the grassland ecosystem. This was achieved by tracking nine GPS-collared hinds over 2 years on a high-country deer farm in Te Anau, Southland, New Zealand. The home ranges of the GPS-tracked hinds varied widely, occupying between 15% and 52% of the total paddock area. Vegetation dominated by naturalised exotic pasture species covered the greatest proportion (>60%) of eight of nine hind home ranges. In contrast, tussock-dominant vegetation coverage was far more variable (0.4–46%), with several indicators suggesting that this vegetation type was used as a substitute for pasture areas under high intra-specific competition among the deer. Both pasture- and tussock-dominant vegetation was used in proportion to its availability. In contrast, shrub-dominated vegetation was used less than its proportional availability, indicating that it was not being put under as much foraging or grazing pressure. This has implications for the further ingression of this vegetation type over time. There was also clear evidence that certain paddock topography was being favoured by the hinds, namely steeper and higher-altitude areas of a paddock. On the basis of these findings, some potential methods for aiding in the management of these extensive tussock grassland paddocks under deer grazing are suggested.