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Indonesia accounts for a large proportion of the oil palm plantation expansion occurring globally. However, Indonesia’s mixed forests (and associated carbon stocks) complicate estimation of the contribution of oil palm agriculture to global carbon budgets. Remotely sensed land-cover classification combined with carbon flux estimates are now used to develop high-resolution estimates of carbon flux from Kalimantan plantations for the period 1990–2010. Oil palm supplies >30% of world vegetable oil production 1 . Plantation expansion is occurring throughout the tropics, predominantly in Indonesia, where forests with heterogeneous carbon stocks undergo high conversion rates 2 , 3 , 4 . Quantifying oil palm’s contribution to global carbon budgets therefore requires refined spatio-temporal assessments of land cover converted to plantations 5 , 6 . Here, we report oil palm development across Kalimantan (538,346 km 2 ) from 1990 to 2010, and project expansion to 2020 within government-allocated leases. Using Landsat satellite analyses to discern multiple land covers, coupled with above- and below-ground carbon accounting, we develop the first high-resolution carbon flux estimates from Kalimantan plantations. From 1990 to 2010, 90% of lands converted to oil palm were forested (47% intact, 22% logged, 21% agroforests). By 2010, 87% of total oil palm area (31,640 km 2 ) occurred on mineral soils, and these plantations contributed 61–73% of 1990–2010 net oil palm emissions (0.020–0.024 GtC yr −1 ). Although oil palm expanded 278% from 2000 to 2010, 79% of allocated leases remained undeveloped. By 2020, full lease development would convert 93,844 km 2 (∼ 90% forested lands, including 41% intact forests). Oil palm would then occupy 34% of lowlands outside protected areas. Plantation expansion in Kalimantan alone is projected to contribute 18–22% (0.12–0.15 GtC yr −1 ) of Indonesia’s 2020 CO 2 -equivalent emissions. Allocated oil palm leases represent a critical yet undocumented source of deforestation and carbon emissions.

Industrial agricultural plantations are a rapidly increasing yet largely unmeasured source of tropical land cover change. Here, we evaluate impacts of oil palm plantation development on land cover, carbon flux, and agrarian community lands in West Kalimantan, Indonesian Borneo. With a spatially explicit land change/carbon bookkeeping model, parameterized using high-resolution satellite time series and informed by socioeconomic surveys, we assess previous and project future plantation expansion under five scenarios. Although fire was the primary proximate cause of 1989–2008 deforestation (93%) and net carbon emissions (69%), by 2007–2008, oil palm directly caused 27% of total and 40% of peatland deforestation. Plantation land sources exhibited distinctive temporal dynamics, comprising 81% forests on mineral soils (1994–2001), shifting to 69% peatlands (2008–2011). Plantation leases reveal vast development potential. In 2008, leases spanned ∼65% of the region, including 62% on peatlands and 59% of community-managed lands, yet <10% of lease area was planted. Projecting business as usual (BAU), by 2020 ∼40% of regional and 35% of community lands are cleared for oil palm, generating 26% of net carbon emissions. Intact forest cover declines to 4%, and the proportion of emissions sourced from peatlands increases 38%. Prohibiting intact and logged forest and peatland conversion to oil palm reduces emissions only 4% below BAU, because of continued uncontrolled fire. Protecting logged forests achieves greater carbon emissions reductions (21%) than protecting intact forests alone (9%) and is critical for mitigating carbon emissions. Extensive allocated leases constrain land management options, requiring trade-offs among oil palm production, carbon emissions mitigation, and maintaining community landholdings.

Commodity crop expansion, for both global and domestic urban markets, follows multiple land change pathways entailing direct and indirect deforestation, and results in various social and environmental impacts. Here we compare six published case studies of rapid commodity crop expansion within forested tropical regions. Across cases, between 1.7% and 89.5% of new commodity cropland was sourced from forestlands. Four main factors controlled pathways of commodity crop expansion: (i) the availability of suitable forestland, which is determined by forest area, agroecological or accessibility constraints, and land use policies, (ii) economic and technical characteristics of agricultural systems, (iii) differences in constraints and strategies between small-scale and large-scale actors, and (iv) variable costs and benefits of forest clearing. When remaining forests were unsuitable for agriculture and/or policies restricted forest encroachment, a larger share of commodity crop expansion occurred by conversion of existing agricultural lands, and land use displacement was smaller. Expansion strategies of large-scale actors emerge from context-specific balances between the search for suitable lands; transaction costs or conflicts associated with expanding into forests or other state-owned lands versus smallholder lands; net benefits of forest clearing; and greater access to infrastructure in already-cleared lands. We propose five hypotheses to be tested in further studies: (i) land availability mediates expansion pathways and the likelihood that land use is displaced to distant, rather than to local places; (ii) use of already-cleared lands is favored when commodity crops require access to infrastructure; (iii) in proportion to total agricultural expansion, large-scale actors generate more clearing of mature forests than smallholders; (iv) property rights and land tenure security influence the actors participating in commodity crop expansion, the form of land use displacement, and livelihood outcomes; (v) intensive commodity crops may fail to spare land when inducing displacement. We conclude that understanding pathways of commodity crop expansion is essential to improve land use governance.

Expansion of the cattle and soy industries in the Amazon basin has increased deforestation rates and will soon push all-weather highways into the region's core. In the face of this growing pressure, a comprehensive conservation strategy for the Amazon basin should protect its watersheds, the full range of species and ecosystem diversity, and the stability of regional climates. Here we report that protected areas in the Amazon basin-the central feature of prevailing conservation approaches-are an important but insufficient component of this strategy, based on policy-sensitive simulations of future deforestation. By 2050, current trends in agricultural expansion will eliminate a total of 40% of Amazon forests, including at least two-thirds of the forest cover of six major watersheds and 12 ecoregions, releasing 32 ± 8 Pg of carbon to the atmosphere. One-quarter of the 382 mammalian species examined will lose more than 40% of the forest within their Amazon ranges. Although an expanded and enforced network of protected areas could avoid as much as one-third of this projected forest loss, conservation on private lands is also essential. Expanding market pressures for sound land management and prevention of forest clearing on lands unsuitable for agriculture are critical ingredients of a strategy for comprehensive conservation.

Background Karuk and Yurok tribes in northwestern California, USA, are revitalizing the practice of cultural burning, which is the use of prescribed burns to enhance culturally important species. These cultural burns are critical to the livelihoods of indigenous peoples, and were widespread prior to the establishment of fire exclusion policies. One of the major objectives of cultural burning is to enhance California hazelnut ( Corylus cornuta Marsh var. californica ) basketry stem production for Karuk and Yurok basketweavers. To evaluate cultural burning as a form of human ecosystem engineering, we monitored hazelnut basketry stem production, qualities, and shrub density in 48 plots (400 m 2 ) within two prescribed and 19 cultural burn sites. Socio-ecological variables that were analyzed included burn frequency, burn season, overstory tree (≥10 cm diameter at breast height) basal area, ungulate browse, and aspect. We also observed basketry stem gathering to compare travel distances, gathering rates, and basketweaver preferences across sites with different fire histories and land tenure. Results Hazelnut shrubs, one growing season post burn, produced a 13-fold increase in basketry stems compared with shrubs growing at least three seasons post burn ( P < 0.0001). Basketry stem production and stem length displayed negative relationships with overstory tree basal area ( P < 0.01) and ungulate browse ( P < 0.0001). Plots burned at high frequency (at least three burn events from 1989 to 2019) had 1.86-fold greater hazelnut shrubs than plots experiencing less than three burn events ( P < 0.0001), and were all located on the Yurok Reservation where land tenure of indigenous people is comparatively stronger. Basketweavers travelled 3.8-fold greater distance to reach gathering sites burned by wildfires compared with those that were culturally burned ( P < 0.01). At cultural burn sites, wildfire sites, and fire-excluded sites, mean gathering rates were 4.9, 1.6, and 0.5 stems per minute per individual, respectively. Conclusions Karuk and Yurok cultural fire regimes with high burn frequencies ( e.g., three to five years) promote high densities of hazelnut shrubs and increase hazelnut basketry stem production. This improves gathering efficiency and lowers travel costs to support the revitalization of a vital cultural practice. Our findings provide evidence of positive human ecosystem engineering, and show that increasing tribal sovereignty over fire management improves socio-economic well-being while at the same time supports measures of ecosystem structure and function.

The burden of proof is being turned upside down With an internationally lauded approach to conserving Southern Ocean ecosystems ( 1 ), the healthiest marine ecosystems on Earth, the Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR), has committed to adopting marine protected areas (MPAs) in the waters around Antarctica ( 2 ). But conflict over MPAs has led CCAMLR member states to disregard the best available science, distort the foundational rules of their convention, break trust, and threaten the integrity of one of the world's most well-regarded science-based multinational governance efforts. With negotiations resuming at the CCAMLR meeting beginning 17 October, we offer recommendations aimed at implementing effective Southern Ocean MPAs, upholding CCAMLR's mandate, and maintaining its global leadership in ecosystem-based management. Given the historic conservation and diplomatic success of CCAMLR and Antarctic governance writ large, if we cannot adopt meaningful MPAs in the Southern Ocean, it does not bode well for doing so in the rest of the high seas.

1. The relative importance of niche- and dispersal-mediated processes in structuring diverse tropical plant communities remains poorly understood. Here, we link mesoscale beta diversity to soil variation throughout a lowland Bornean watershed underlain by alluvium, sedimentary and granite parent materials (c. 340 ha, 8-200 m a.s.l.). We test the hypothesis that species turnover across the habitat gradient reflects interspecific partitioning of soil resources. 2. Floristic inventories (greater than or equal to 1 cm d.b.h.) of the Dipterocarpaceae, the dominant Bornean canopy tree family, were combined with extensive soil analyses in 30 (0.16 ha) plots. Six samples per plot were analysed for total C, N, P, K, Ca and Mg, exchangeable K, Ca and Mg, extractable P, texture, and pH. 3. Extractable P, exchangeable K, and total C, N and P varied significantly among substrates and were highest on alluvium. Thirty-one dipterocarp species (n = 2634 individuals, five genera) were recorded. Dipterocarp density was similar across substrates, but richness and diversity were highest on nutrient-poor granite and lowest on nutrient-rich alluvium. 4. Eighteen of 22 species were positively or negatively associated with parent material. In 8 of 16 abundant species, tree distribution (greater than or equal to 10 cm d.b.h.) was more strongly non-random than juveniles (1-10 cm d.b.h.), suggesting higher juvenile mortality in unsuitable habitats. The dominant species Dipterocarpus sublamellatus (> 50% of stems) was indifferent to substrate, but nine of 11 'subdominant' species (> 8 individuals ha(-1)) were substrate specialists. 5. Eighteen of 22 species were significantly associated with soil nutrients, especially P, Mg and Ca. Floristic variation was significantly correlated with edaphic and geographical distance for all stems greater than or equal to 1 cm d.b.h. in Mantel analyses. However, juvenile variation (1-10 cm d.b.h.) was more strongly related to geographical distance than edaphic factors, while the converse held for established trees (greater than or equal to 10 cm d.b.h.), suggesting increased importance of niche processes with size class. 6. Pervasive dipterocarp associations with soil factors suggest that niche partitioning structures dipterocarp tree communities. Yet, much floristic variation unrelated to soil was correlated with geographical distance between plots, suggesting that dispersal and niche processes jointly determine mesoscale beta diversity in the Bornean Dipterocarpaceae.

Studies on the relationship between soil fertility and aboveground biomass in lowland tropical forests have yielded conflicting results, reporting positive, negative and no effect of soil nutrients on aboveground biomass. Here, we quantify the impact of soil variation on the stand structure of mature Bornean forest throughout a lowland watershed (8-196 m a.s.l.) with uniform climate and heterogeneous soils. Categorical and bivariate methods were used to quantify the effects of (1) parent material differing in nutrient content (alluvium > sedimentary > granite) and (2) 27 soil parameters on tree density, size distribution, basal area and aboveground biomass. Trees >=10 cm (diameter at breast height, dbh) were enumerated in 30 (0.16 ha) plots (sample area = 4.8 ha). Six soil samples (0-20 cm) per plot were analyzed for physiochemical properties. Aboveground biomass was estimated using allometric equations. Across all plots, stem density averaged 521 ± 13 stems ha-¹, basal area 39.6 ± 1.4 m² ha-¹ and aboveground biomass 518 ± 28 Mg ha-¹ (mean ± SE). Adjusted forest-wide aboveground biomass to account for apparent overestimation of large tree density (based on 69 0.3-ha transects; sample area = 20.7 ha) was 430 ± 25 Mg ha-¹. Stand structure did not vary significantly among substrates, but it did show a clear trend toward larger stature on nutrient-rich alluvium, with a higher density and larger maximum size of emergent trees. Across all plots, surface soil phosphorus (P), potassium, magnesium and percentage sand content were significantly related to stem density and/or aboveground biomass (R Pearson = 0.368-0.416). In multiple linear regression, extractable P and percentage sand combined explained 31% of the aboveground biomass variance. Regression analyses on size classes showed that the abundance of emergent trees >120 cm dbh was positively related to soil P and exchangeable bases, whereas trees 60-90 cm dbh were negatively related to these factors. Soil fertility thus had a significant effect on both total aboveground biomass and its distribution among size classes.

Tropical deforestation released similar to 1.5 billion metric tons of carbon (GtC) to the atmosphere annually throughout the 1990s, accounting for almost 20% of anthropogenic greenhouse gas emissions. Without implementation of effective policies and measures to slow deforestation, clearing of tropical forests will likely release an additional 87 to 130 GtC by 2100, corresponding to the carbon release of more than a decade of global fossil fuel combustion at current rates. Drought-induced tree mortality, logging, and fire may double these emissions, and loss of carbon uptake (i.e., sink capacity) as forest area decreases may further amplify atmospheric CO sub(2) levels.

Biomass burning plays a critical role not only in atmospheric emissions, but also in the deposition and redistribution of biologically important nutrients within tropical landscapes. We quantified the influence of fire on biogeochemical fluxes of nitrogen (N), phosphorus (P), and sulfur (S) in a 12 ha forested peatland in West Kalimantan, Indonesia. Total (inorganic + organic) N, NO 3 − -N, NH 4 + -N, total P, PO 4 3 − -P, and SO 4 2 − -S fluxes were measured in throughfall and bulk rainfall weekly from July 2013 to September 2014. To identify fire events, we used concentrations of particulate matter (PM10) and MODIS Active Fire Product counts within 20 and 100 km radius buffers surrounding the site. Dominant sources of throughfall nutrient deposition were explored using cluster and back-trajectory analysis. Our findings show that this Bornean peatland receives some of the highest P (7.9 kg PO 4 3 − -P ha−1yr−1) and S (42 kg SO 4 2 − -S ha−1yr−1) deposition reported globally, and that N deposition (8.7 kg inorganic N ha−1yr−1) exceeds critical load limits suggested for tropical forests. Six major dry periods and associated fire events occurred during the study. Seventy-eight percent of fires within 20 km and 40% within 100 km of the site were detected within oil palm plantation leases (industrial agriculture) on peatlands. These fires had a disproportionate impact on below-canopy nutrient fluxes. Post-fire throughfall events contributed >30% of the total inorganic N ( NO 3 − -N + NH 4 + -N) and PO 4 3 − -P flux to peatland soils during the study period. Our results indicate that biomass burning associated with agricultural peat fires is a major source of N, P, and S in throughfall and could rival industrial pollution as an input to these systems during major fire years. Given the sheer magnitude of fluxes reported here, fire-related redistribution of nutrients may have significant fertilizing or acidifying effects on a diversity of nutrient-limited ecosystems.