Community structure dynamics and carbon stock change of rehabilitated mangrove forests in Sulawesi, Indonesia

Abstract

To date, discourse associated with the potential application of “blue carbon” within real‐world carbon markets has focused on blue carbon as a mitigation strategy in the context of avoided deforestation (e.g., REDD+). Here, we report structural dynamics and carbon storage gains from mangrove sites that have undergone rehabilitation to ascertain whether reforestation can complement conservation activities and warrant project investment. Replicated sites at two locations with contrasting geomorphic conditions were selected, Tiwoho and Tanakeke on the island of Sulawesi, Indonesia. These locations are representative of high (Tiwoho, deep muds and silty substrates) and low (Tanakeke, shallow, coralline sands) productivity mangrove ecosystems. They share a similar management history of clearing and conversion for aquaculture before restorative activities were undertaken using the practice of Ecological Mangrove Rehabilitation (EMR). Species diversity and mean biomass carbon storage gains after 10 yr of regrowth from the high productivity sites of Tiwoho (49.2 ± 9.1 Mg C·ha−1·yr−1) are already almost of one‐third of mean biomass stocks exhibited by mature forests (167.8 ± 30.3 Mg C·ha−1·yr−1). Tiwoho's EMR sites, on average, will have offset all biomass C that was initially lost through conversion within the next 11 yr, a finding in marked contrast to the minimal carbon gains observed on the low productivity, low diversity, coral atoll EMR sites of Tanakeke (1.1 ± 0.4 Mg C·ha−1·yr−1). These findings highlight the importance of geomorphic and biophysical site selection if the primary purpose of EMR is intended to maximize carbon sequestration gains.

Mangrove blue carbon stocks and dynamics are controlled by hydrogeomorphic settings and land‐use change

“…This study shows that mangrove restoration, if conducted at an adequate scale, has the potential to contribute to Indonesia's NDCs by increasing mangrove carbon stocks and offsetting anthropogenic GHG emissions. This has also been shown at the site scale for other parts of Indonesia (Cameron et al, 2019). There is growing interest in utilizing carbon removals by mangroves in Indonesia and elsewhere to finance restoration activities, by trading carbon credits through the Kyoto Protocol's Clean Development Mechanism or voluntary Payments for Ecosystem Services schemes (Locatelli et al, 2014).…”

“…When carbon emissions associated with mangrove land‐use change are not separately calculated, the magnitude of this ecosystems’ impact on GHG emission management may be underestimated. While previous blue carbon knowledge gaps in Indonesia were associated with the availability of suitable emissions factor data (Murdiyarso et al, 2018), findings and data from this study, along with other studies from other islands such as Kalimantan (Arifanti et al, 2019) and Sulawesi (Cameron, Hutley, Friess, & Brown, 2019), could be used by policymakers to develop science‐based policy and manage blue carbon emissions abatement at the national scale.…”

The role of fungi in heterogeneous sediment microbial networks

“…Environmental variability guides the assembly of sediment bacteria and archaea by creating a halo of sequential physio-chemical characteristics around macrofaunal burrows, but here we suggest that key species detected by the study of the interactome also have an important effect on community assembly by driving co-occurrence patterns among microbial species. Understanding this complex relationship could be of pivotal importance in the comprehension of ecosystem functioning and restoration, especially for intertidal systems 46 . Combined, environmental factors and microbial species interactions can create new niches that boost microbial community diversity, stability and resilience through functional redundance 47,48 .…”

Mangrove Rehabilitation and Restoration as Experimental Adaptive Management

“…Rehabilitated mangroves sequester more C than the land-use cover-types they replace (Sasmito et al, 2019). Successful rehabilitation has led to rapid accumulation of biomass C stocks, and over longer time scales can increase soil carbon stocks by 83 (Matsui et al, 2012) to 96 Mg C/ha (Cameron et al, 2019a). Rehabilitated mangroves on previously abandoned and exposed aquaculture ponds emit substantially less CO 2 from their soils than do the abandoned, exposed ponds themselves (Cameron et al, 2019a).…”

“…Successful rehabilitation has led to rapid accumulation of biomass C stocks, and over longer time scales can increase soil carbon stocks by 83 (Matsui et al, 2012) to 96 Mg C/ha (Cameron et al, 2019a). Rehabilitated mangroves on previously abandoned and exposed aquaculture ponds emit substantially less CO 2 from their soils than do the abandoned, exposed ponds themselves (Cameron et al, 2019a). In parallel, rates of peat accumulation in constructed mangrove forests can exceed that of natural stands (Osland et al, 2020).…”