Local Management of Mangrove Forests in the Philippines: Successful Conservation or Efficient Resource Exploitation?

Recent environmental narratives suggest that local people are effective stewards of forest resources. Local restoration and management of mangrove forests, in particular, are now widely advocated as a solution to achieve both economic and environmental conservation goals. This paper presents findings from a study of 2 coastal sites in the Philippines that are renowned and often showcased as success stories in community-based, mangrove reforestation and management. These cases are especially intriguing because local tree planting and management emerged in both areas long before governments and nongovernment organizations began to promote such activities. These management systems are a successful economic innovation in that planted mangroves protect homes and fish pond dykes from wave and wind damage, and the production of high-value construction wood is dramatically enhanced through intensive plantation management. Mangrove plantations are an efficient alternative to harvesting from unplanted, natural mangroves and their spread may reduce harvesting pressures on existing forests. However, mangrove plantations are structurally and compositionaly very different from unplanted forests, a finding of particular concern given that such plantations are increasingly encroaching into and replacing natural forests. Furthermore, planted forests are not typically viewed by planters in terms of their environmental conservation values and are frequently cut and cleared to make space for alternative uses, especially fish farming and residential settlement. The suggestion that these local mangrove management systems are successful for conservation thus needs to be qualified.     

Utilization of mangrove wood products around mida creek (Kenya) amongst subsistence and commercial users

Mida Creek (Kenya) comprises mangrove forests and other marine resources that are of economic, ecological, and environmental importance to the local village communities. In total 116 households (100 of which could be used for numerical analysis), which are estimated to correspond to a coverage of ca. 30% of the total Mida Creek population, were interviewed to assess the human reliance on mangrove resources in Mida Creek. The survey indicates that mangroves are a major resource of wood for house construction, fuel wood, charcoal, and boat building. Minor uses of mangrove products include pharmaceutical and medicinal applications, tanning material, and furniture making. Rhizophora mucronata, Ceriops tagal, and Bruguiera gymnorrhiza are the major resources for house construction and fuel wood, while Sonneratia alba and Xylocarpus granatum were reported to be useful for boat building and medicinal uses respectively. The survey further describes harvesting activities and house construction, and reveals species preferences within this one particular use. As a result of depletion of the supply and the banning of mangrove harvesting, the local people are turning to other wood materials and to poaching. In our view, local utilization patterns rather than global usefulness data are required to establish a conservation policy of both mangroves and users’ subsistence requirements.     

Tracking Human Disturbance in Mangroves: Estimating Harvest Rates on a Micronesian Island

Disturbance is an integral component in mangrove forest dynamics, influencing forest structure, composition, and function. The impacts of human disturbance, however, threaten mangrove forests throughout the world. Small-scale wood harvesting on the small Pacific island of Kosrae, Federated States of Micronesia, provided an instructive scenario for exploring the dynamics of human disturbance. Natural disturbances on the island are rare, but the growing island population harvests mangrove trees for firewood and construction materials, placing pressure on the forest. In order to determine recent harvest rates, we estimated gap ages by developing a time scale for mangrove wood decomposition and by quantifying growth rates for Rhizophora apiculata and Bruguiera gymnorhiza seedlings. Stump and log decomposition patterns were useful in aging gaps, although some patterns were more reliable than others. Seedlings of both species added approximately 5 nodes/year depending on light conditions. The island-wide harvest rate was 10% over the last 10 years, but the rates varied widely among different parts of the island. Rhizophora apiculata has been harvested preferentially, and a dearth of young trees where harvesting has been heaviest portends a decline of this highly desired species in the forest. Socio-economic data substantiated some but not all of the trends we observed. Even on a small island, local differences in both natural and anthropogenic factors are important to understanding forest dynamics.     

Ethnobiology, socio-economics and management of mangrove forests: A review

There is growing research interest in the ethnobiology, socio-economics and management of mangrove forests. Coastal residents who use mangroves and their resources may have considerable botanical and ecological knowledgeable about these forests. A wide variety of forest products are harvested in mangroves, especially wood for fuel and construction, tannins and medicines. Although there are exceptions, mangrove forest products are typically harvested in a small-scale and selective manner, with harvesting efforts and impacts concentrated in stands that are closer to settlements and easiest to access (by land or by sea). Mangroves support diverse, local fisheries, and also provide critical nursery habitat and marine productivity which support wider commercial fisheries. These forests also provide valuable ecosystem services that benefit coastal communities, including coastal land stabilization and storm protection. The overlapping of marine and terrestrial resources in mangroves creates tenure ambiguities that complicate management and may induce conflict between competing interests. Mangroves have been cut and cleared extensively to make way for brackish water aquaculture and infrastructure development. More attention is now given to managing remaining forests sustainably and to restoring those degraded from past use. Recent advances in remotely sensed, geo-spatial monitoring provide opportunities for researchers and planners to better understand and improve the management of these unique forested wetlands.     

Plants and traditional knowledge: An ethnobotanical investigation on Monte Ortobene (Nuoro, Sardinia)

Background

Worldwide there is growing research interest in the ethnobiology of mangrove forests. Notwithstanding that, little information has been published about ethnobiology of mangrove forests in Cameroon. The aims of this study were a) to analyze the harvesting methods and the local selling of mangrove wood products by loggers in the vicinity of Wouri estuary and b) to investigate the patterns of subsistence uses of mangrove wood products around the Douala-Edea reserve.

Methods

Semi-structured interviews were conducted with 120 active mangrove loggers in 23 Douala wood markets and 103 households located in three villages (Mbiako, Yoyo I and Yoyo II) close to Douala-Edea reserve. In each of the three densely populated villages, every second household was chosen for sampling while in all markets, mangrove loggers were chosen randomly. In addition, log diameters were measured in each market using a wooden foldable tape measure. A post hoc analysis (Newman-Keuls test) was performed in order to detect the common wood class diameter sold in the Douala wood markets.

Results

The analysis of the loggers' survey data has shown that large logs of Rhizophora with diameter greater than 40 cm were common in the Douala wood markets and were more closely associated with loggers who used chainsaws. In addition to the general mangroves wood products selling, the analysis on a subsistence level (households' survey) suggests the local population's dependence on mangroves, with multiple uses of Rhizophora racemosa Meyer, R. harrisonii Leechman, Avicennia germinans L. Stearn., Laguncularia racemosa Gaertn. f. and Conocarpus erectus L. timbers for furniture, fences, smoking fish, and fuelwood. Finally, Nypa fruticans (Thunb.) Wurmb. leaves were used as thatching material for house walls and roofs.

Conclusion

Our findings revealed that big logs of Rhizophora were commonly sold by the loggers. A majority of loggers (60%) reported that mangrove marketed wood constitute a principal source of income. Most of the villagers (85.83%) often depend on mangroves for subsistence needs and for them there is no substitute for mangrove wood. Therefore, more efforts should be undertaken at the national level to implement conservation, management and sustainable use of these coastal forests.     

Poverty and institutional management stand-off: a restoration and conservation dilemma for mangrove forests of Tanzania

Mangrove forests of Tanzania are reserved by law, but the capacity to effectively enforce this institution has remained far from reach and mangrove forests continue to be exploited as cheap sources of wood and forest land for other uses. Often, the rural poor who depend on mangroves for their subsistence are pointed out by the state institutions as culprits of the degradation. Promisingly though, this paradigm is being offset by the emerging positive view about human proclivity for caring and nurturing common resources. Traditional and community based forest management practices are emerging as appropriate alternatives to state control and institutional arrangement for ensuring sustainable management of forest resources. Nonetheless, community based management has not yet been robustly implemented for mangrove forests in Tanzania. Retrospectively, this paper argues that nationalization of mangrove forests has not been successful in reversing mangrove degradation. The experiences have instead been the frictions between people and the state, as desperate rural poor continue to plunder on and make a living at the expense of mangrove forests. The paper exemplify how policy failure, weak or dysfunctional state institutions in Tanzania compounded by little participatory awareness and self commitment are ruining the restoration and conservation initiatives.     

Environmental Effects of Canopy Gap Formation in High-Rainfall Mangrove Forests1

This study investigated the importance of gap formation in mangrove swamps on the island of Kosrae, Federated States of Micronesia, in order to understand better both natural processes of forest development and the effects of harvesting trees for firewood in these wetlands. Measurements were concentrated in seven plots located near four rivers: three in fringe zones and four in basin zones. Each plot was a cluster of five points and covered an area of ca 1.3 ha. From every point in each of the seven plots, the nearest canopy gap ≥10 m² was located; 25 of the 35 gaps were formed by harvesting. Porewater salinity was significantly higher under the canopy in fringe mangrove forests than in basin mangrove forests. Although gaps were small (mean gap size = 158 m²; median gap size = 92 m²), soil temperatures were significantly higher in gaps of both zones. Soil redox potential was significantly lower and porewater salinity significantly higher in the gaps than under the canopy in the basin zone only. Higher porewater salinity may be attributed to high evaporation rates from the soil and high transpiration rates from trees surrounding gaps. There were significantly more seedlings in gaps than under the canopy only in the fringe zones. Although gap formation alters the soil environment of Kosraean mangrove swamps, high freshwater input may buffer these effects in basin mangrove swamps by reducing porewater salinity. Current harvesting rates do not appear to be changing canopy species composition, but large gaps, especially in mangrove forests in more arid areas, may lead to major changes.     

Short-term impacts of energy wood harvesting on ectomycorrhizal fungal communities of Norway spruce saplings

The increased demand for harvesting energy wood raises questions about its effects on the functioning of the forest ecosystems, soil processes and biodiversity. Impacts of tree stump removal on ectomycorrhizal fungal (EMF) communities of Norway spruce saplings were studied with 454-pyrosequencing in a 3-year field experiment replicated in 3 geographical areas. This is possibly the most thorough investigation of EMF communities associated with saplings grown on sites subjected to energy wood harvesting. To separate impacts of tree stump and logging residue removal on EMF and plant variables, we used three harvesting treatments with increasing complexity from patch mounding alone (P) to patch mounding combined with logging residue removal (RP), and patch mounding combined with both logging residue and stump removal (SRP). Saplings grown in uncut forests (F) served as references for harvesting treatments. A majority of sequences (>92%) and operational taxonomic units (OTUs, 55%) were assigned as EMF. EMF OTU richness, fungal community composition or sapling growth did not differ between harvesting treatments (P, RP and SRP), while EMF OTU richness, diversity and evenness were highest and sapling growth lowest in the undisturbed reference forests (F). The short study period may partially explain the similarities in fungal and sapling variables in different harvesting treatments. In conclusion, our results indicate that neither stump removal nor logging residue removal have significant additional negative impacts on EMF communities or growth of Norway spruce saplings in the short-term compared with the impacts of more conventional harvesting methods, including clear cutting and patch mounding.     

Ecological engineering for successful management and restoration of mangrove forests

Great potential exists to reverse the loss of mangrove forests worldwide through the application of basic principles of ecological restoration using ecological engineering approaches, including careful cost evaluations prior to design and construction. Previous documented attempts to restore mangroves, where successful, have largely concentrated on creation of plantations of mangroves consisting of just a few species, and targeted for harvesting as wood products, or temporarily used to collect eroded soil and raise intertidal areas to usable terrestrial agricultural uses. I document here the importance of assessing the existing hydrology of natural extant mangrove ecosystems, and applying this knowledge to first protect existing mangroves, and second to achieve successful and cost-effective ecological restoration, if needed. Previous research has documented the general principle that mangrove forests worldwide exist largely in a raised and sloped platform above mean sea level, and inundated at approximately 30%, or less of the time by tidal waters. More frequent flooding causes stress and death of these tree species. Prevention of such damage requires application of the same understanding of mangrove hydrology.     

Plant-animal interactions and the structure and function of mangrove forest ecosystems*

Trophic interactions involving plants and animals in tropical mangrove forests have important controlling influences on several population, community and ecosystem-level processes. Insect herbivores remove up to 35% of leaf area from some mangrove tree species and can cause the death of seedlings. Leaf chemistry and toughness and soil nutrient status all appear to be important in explaining the between- and among-species variance in leaf damage. Insects also attack and damage, mainly by boring, a large proportion of mangrove seeds. Shadehouse experiments have shown that such post-dispersal predation can have a significant effect on seedling survival, growth and biomass allocation to leaves, stems and roots. Sesarmid crabs are also responsible for severe post-dispersal seed predation. In field trials, crabs consumed more than 70% of the seeds of five tree species. For four of these five species there was an inverse relationship between seed predation rate and the dominance of conspecific adult trees, while the within-site distribution pattern of one tree species appears to be partially controlled by crabs. The same crab species also consume 30–80% (depending on forest type and intertidal elevation), of the annual litter fall in mangrove forests and, thus, have an important role in controlling the rate of remineralization of detritus within forests and the export of particulate matter from the forests to other nearshore habitats. The other major component of litter in the forests is wood, which is broken down relatively rapidly by teredinid molluscs (shipworms). More than 90% of the weight loss from decomposing trunks of Rhizophora species during the first four years of decay is through ingestion by teredinids. The annual turnover of dead wood mass in Rhizophora forests is equivalent to that of the processing of leaf detritus by crabs. Because of the relatively low species richness of trees and consumers in tropical mangrove forests, they are likely to serve as productive sites for further investigations of the influence of plant-animal interactions on the dynamics of tropical forests.     

Status and exploitation of the mangrove and associated fishery resources in Zanzibar

The distribution and growth forms of the mangroves on Zanzibar island (Unguja and Pemba) were investigated. Pemba island, with approximately 12000 ha of mangroves, had nine species; and Unguja island, with 6 000 ha, had eight. Average cropping intensities in Pemba island varied between 350–1937 cut plants per ha while in Unguja these were between 777–3567 cut plants per ha. In Pemba, mangrove forests were relatively less heavily exploited compared to those in Unguja, where clear felling was common. Charcoal, lime and salt production are the major activities which involve heavy utilization of mangrove wood.The fishery resources (shellfish and finfish) associated with the mangrove vegetation were also investigated by examining the composition of fish catches at landing stations in mangrove as well as nonmangrove zones of fishing districts. A survey on the fauna associated with mangrove forests was also conducted. A number of the local commercial fish species were found to be associated with the mangrove vegetation. The fishes of the genusLethrinus and the rabbit fishSiganus were found to constitute the bulk of the fish caught from waters adjacent to mangroves using movable traps. The molluscPyrazus sp., which is commonly used by the local people for food and bait, was found only in the mangroves.     

Valuing mangrove ecosystem services: linking nutrient retention function of mangrove forests to enhanced agroecosystem production

Mangroves are highly productive wetland ecosystems strategically located at the interface between land and sea. They play an important role in the biogeochemical cycles of the coastal environment, acting as sources of nutrients to adjacent marine and terrestrial ecosystems through active and passive transport. We examined the nutrient contents in mangrove and nonmangrove soils in and around the Bhitarkanika National Park, India and assessed whether the local agricultural producers were aware of and placed a value on this contribution of mangrove forests in enhancing agroecosystem productivity. Soil samples from both mangrove and nonmangrove areas were analysed and quantity of organic carbon, total nitrogen, available phosphorus and potassium were derived. The replacement cost method was used to derive the value of nutrients in mangrove soils. We estimated that each hectare of mangrove contains additional nutrients worth US$232.49 in comparison to nonmangrove areas. The difference in nutrient content in mangrove versus nonmangrove areas gave the value of US$3.37 million for the nutrients in 145 km² of mangrove forests. The agricultural producers were aware that mangrove forests act as a source of nutrients and were willing to pay a higher price for the land adjoining mangrove forests. Around 92% of the producers ranked nutrient retention as a secondary function of mangrove forests. Despite crop depredation from wild ungulates and conflict with salt water crocodiles the agriculturist finds the benefit to cost ratio of mangrove forests high and more than 76% were in favour of mangrove restoration. This study provides an opportunity to highlight the importance of mangrove ecosystems to the livelihoods of the local people and the urgent need to sustain these through proper policy and market interventions.     

Local Mangrove Planting in the Philippines: Are Fisherfolk and Fishpond Owners Effective Restorationists?

Local fisherfolk and fishpond owners have been practicing “restoration” of mangrove forests in some parts of the Philippines for decades, well before governments and non‐government organizations began to promote the activity as a conservation tool. This paper examines ecological characteristics of these mangrove plantations and compares them to natural mangroves in the same areas. Mangrove planters were interviewed and plantation and natural mangrove forests were surveyed to measure forest structure, composition and regeneration. Compared with natural forests, mangrove plantations were characterized by high densities of small stems, shorter and narrower canopies, and fewer species. For both economic and ecological reasons, the vast majority of people dispersed and planted only Rhizophora mucronata/stylosa and, furthermore, they often thinned other species out of planted areas. There was remarkably little subsequent recruitment of other, nonplanted mangrove species into plantations up to 50 and 60 years of age. This pattern held across a diversity of sites, including plantations that had not been selectively cut or weeded. Important ecological and economic benefits result from local mangrove planting, but catalyzing diverse forest regeneration—at least in the short to medium term—is not one of them. The lesson: if you want to restore diverse mangrove forests, you have to plant diverse mangrove forests.     

Mimicking natural disturbances of boreal forests: the effects of controlled burning and creating dead wood on beetle diversity

The young successional stages of boreal forests are an important habitat for many saproxylic species. These habitats are formed by disturbances such as forest fires and they are characterized by large volumes of dead wood and sun-exposed conditions. Today, young successional stages of natural origin are very rare in Fennoscandia and there is need for restoration. We constructed a large-scale field experiment in which we studied the effects of two restoration practices on beetle diversity: controlled burning and partial harvesting with creating different volumes of dead wood. We sampled beetles with flight-intercept traps recording a total of 56,031 individuals and 755 species. The species richness and abundance of both saproxylic and non-saproxylic beetles were increased by burning and harvesting but the volume of dead wood created on harvested sites had no short-term effect on species richness or abundance. Rare species, especially saproxylic ones, preferred burned sites and a similar trend was observed among red-listed and pyrophilous species. Burning and harvesting also resulted in different species assemblages and there were some additional differences according to the volume of dead wood. We conclude that fire can be successfully used in restoration of managed boreal forests to increase species diversity and to facilitate the recovery of declined species. However, long-term monitoring is needed to clarify the effects of the restoration practices, in particular those of creating dead wood without using fire.     

Effects of harvesting on spatial and temporal diversity of carbon stocks in a boreal forest landscape

Carbon stocks in managed forests of Ontario, Canada, and in harvested wood products originated from these forests were estimated for 2010–2100. Simulations included four future forest harvesting scenarios based on historical harvesting levels (low, average, high, and maximum available) and a no‐harvest scenario. In four harvesting scenarios, forest carbon stocks in Ontario's managed forest were estimated to range from 6202 to 6227 Mt C (millions of tons of carbon) in 2010, and from 6121 to 6428 Mt C by 2100. Inclusion of carbon stored in harvested wood products in use and in landfills changed the projected range in 2100 to 6710–6742 Mt C. For the no‐harvest scenario, forest carbon stocks were projected to change from 6246 Mt C in 2010 to 6680 Mt C in 2100. Spatial variation in projected forest carbon stocks was strongly related to changes in forest age (r = 0.603), but had weak correlation with harvesting rates. For all managed forests in Ontario combined, projected carbon stocks in combined forest and harvested wood products converged to within 2% difference by 2100. The results suggest that harvesting in the boreal forest, if applied within limits of sustainable forest management, will eventually have a relatively small effect on long‐term combined forest and wood products carbon stocks. However, there was a large time lag to approach carbon equality, with more than 90 years with a net reduction in stored carbon in harvested forests plus wood products compared to nonharvested boreal forest which also has low rates of natural disturbance. The eventual near equivalency of carbon stocks in nonharvested forest and forest that is harvested and protected from natural disturbance reflects both the accumulation of carbon in harvested wood products and the relatively young age at which boreal forest stands undergo natural succession in the absence of disturbance.     

Radiocarbon Dating and Wood Density Chronologies of Mangrove Trees in Arid Western Australia

Mangrove trees tend to be larger and mangrove communities more diverse in tropical latitudes, particularly where there is high rainfall. Variation in the structure, growth and productivity of mangrove forests over climatic gradients suggests they are sensitive to variations in climate, but evidence of changes in the structure and growth of mangrove trees in response to climatic variation is scarce. Bomb-pulse radiocarbon dating provides accurate dates of recent wood formation and tree age of tropical and subtropical tree species. Here, we used radiocarbon techniques combined with X-ray densitometry to develop a wood density chronology for the mangrove Avicennia marina in the Exmouth Gulf, Western Australia (WA). We tested whether wood density chronologies of A. marina were sensitive to variation in the Pacific Decadal Oscillation Index, which reflects temperature fluctuations in the Pacific Ocean and is linked to the instrumental rainfall record in north WA. We also determined growth rates in mangrove trees from the Exmouth Gulf, WA. We found that seaward fringing A. marina trees (∼10 cm diameter) were 48±1 to 89±23 years old (mean ± 1σ) and that their growth rates ranged from 4.08±2.36 to 5.30±3.33 mm/yr (mean ±1σ). The wood density of our studied mangrove trees decreased with increases in the Pacific Decadal Oscillation Index. Future predicted drying of the region will likely lead to further reductions in wood density and their associated growth rates in mangrove forests in the region.     

Short‐term effect of selection cutting in boreal balsam fir forest on cerambycid and scolytid beetles

The ecology and management of boreal forest ecosystems are drawing greater attention worldwide as their importance is being increasingly recognized for carbon sequestration or for harbouring the world's largest remaining intact forests. Selection cuts have been introduced as a more socially acceptable silvicultural method to improve the maintenance of habitat structure and functions as they mimic aspects of boreal forest succession dynamics. Many studies have shown that selection cutting helps maintaining arthropod communities in mature forests, but few have examined the increased risks of damage by bark‐ and wood‐boring insects in boreal forests of eastern North America. We used multidirectional flight‐interception traps to quantify the response of these beetles to 25 and 40% selection cutting in a balsam fir–white birch forest of Québec, Canada. The abundance and species number of both cerambycid and scolytid beetles were 5–6 times larger in selectively cut stands than in controls the year following treatments. Analyses revealed that bark‐ and wood‐boring beetles’ response was mostly associated with increased canopy openness in selectively cut stands (and sun‐exposed locations within them) and residual tree injuries caused by harvesting operations. These conditions attracted beetles such as Trypodendron lineatum (Scolytinae) and Rhagium inquisitor (Cerambycidae), two species known for their ability to attack weakened, dying and dead hosts. Most species were more abundant in selection cuts, except for Evodinus m. monticola (Cerambycidae) whose abundance was strongly reduced after treatment. Some beetles can have detrimental effects on residual trees and thus could reduce timber value, but most species found in treated stands do not represent a high risk for healthy trees. Thus, selection cuts do not seem favourable to the establishment of tree‐killing beetles. However, as they were found more active/abundant after selection cutting, it would be wise to further study their population dynamics over mid‐ and long‐term periods, along with the ecological and economic implications associated with this silvicultural treatment.     

Long-Term Impacts of Fuelwood Extraction on a Tropical Montane Cloud Forest

Fuelwood extracted from natural forests serves as a principal energy source in rural regions of many tropical countries. Although fuelwood extraction (even low intensities) might strongly impact the structure and species composition of natural forests, long-term studies remain scarce. Here, we estimate the potential long-term impacts (over several hundred years) of such repeated harvesting of single trees on tropical montane cloud forest in central Veracruz, Mexico, by applying a process-based forest growth model. We simulate a wide range of possible harvesting scenarios differing in wood volume harvested and preferred tree species and sizes, and use a set of indicators to compare their impacts on forest size structure and community composition. Results showed that the overall impact on forest structure and community composition increased linearly with the amount of harvested wood volume. Even at low levels of harvesting, forest size structure became more homogeneous in the long term because large old trees disappeared from the forest, but these changes might take decades or even centuries. Although recruitment of harvested species benefited from harvesting, species composition shifted to tree species that are not used for fuelwood. Our results demonstrate that fuelwood extraction can have marked long-term impacts on tropical montane cloud forests. The results also offer the possibility to support the design of management strategies for the natural species-rich forests that achieve a balance between economic needs and ecological goals of the stakeholders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Sustainable management of planted landscapes: lessons from Japan

In Japan, 42?% of forests are planted forests, and most of them were established after World War II (1950–1980) to meet increased wood demands. Although Japanese planted forests are now reaching their planned harvest age, they have not been managed, and their restoration is now being discussed. Japanese foresters have not cut their own forests, and the country’s high wood demands have been met by imports during recent decades. The decline of young forests due to the stagnation of forestry activity is suggested to be partly responsible for the nation-wide decline in early-successional species, which is referred to as the “second crisis of biodiversity.” As a timber-importing nation, it is suggested that Japan has underused the nation’s own forests and has overused forests elsewhere. A revival of Japanese plantation forestry may contribute to the restoration of early-successional species because young planted forests are likely to provide suitable habitats. Furthermore, only 30?% of the current planted forests in Japan will be needed to meet the expected future domestic demand for lumber and plywood without imports. The remaining 70?% of the current planted forests may be restored to natural forests with or without harvesting. The history of Japanese planted forests suggests that some natural trees/forests should be retained, even in the landscapes that specialize in wood production, because part of the planted forests may be economically marginalized in the future, and their restoration to natural forests would then be needed.     

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

Globally, carbon‐rich mangrove forests are deforested and degraded due to land‐use and land‐cover change (LULCC). The impact of mangrove deforestation on carbon emissions has been reported on a global scale; however, uncertainty remains at subnational scales due to geographical variability and field data limitations. We present an assessment of blue carbon storage at five mangrove sites across West Papua Province, Indonesia, a region that supports 10% of the world's mangrove area. The sites are representative of contrasting hydrogeomorphic settings and also capture change over a 25‐years LULCC chronosequence. Field‐based assessments were conducted across 255 plots covering undisturbed and LULCC‐affected mangroves (0‐, 5‐, 10‐, 15‐ and 25‐year‐old post‐harvest or regenerating forests as well as 15‐year‐old aquaculture ponds). Undisturbed mangroves stored total ecosystem carbon stocks of 182–2,730 (mean ± SD: 1,087 ± 584) Mg C/ha, with the large variation driven by hydrogeomorphic settings. The highest carbon stocks were found in estuarine interior (EI) mangroves, followed by open coast interior, open coast fringe and EI forests. Forest harvesting did not significantly affect soil carbon stocks, despite an elevated dead wood density relative to undisturbed forests, but it did remove nearly all live biomass. Aquaculture conversion removed 60% of soil carbon stock and 85% of live biomass carbon stock, relative to reference sites. By contrast, mangroves left to regenerate for more than 25 years reached the same level of biomass carbon compared to undisturbed forests, with annual biomass accumulation rates of 3.6 ± 1.1 Mg C ha^?1 year^?1. This study shows that hydrogeomorphic setting controls natural dynamics of mangrove blue carbon stocks, while long‐term land‐use changes affect carbon loss and gain to a substantial degree. Therefore, current land‐based climate policies must incorporate landscape and land‐use characteristics, and their related carbon management consequences, for more effective emissions reduction targets and restoration outcomes.