Lisa M. Curran

Modelling conservation in the Amazon basin

Expansion of the cattle and soy industries in the Amazon basin has increased deforestation rates and will soon push all-weather highways into the regions 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.

Committed carbon emissions, deforestation, and community land conversion from oil palm plantation expansion in West Kalimantan, Indonesia.

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.

SEED DISPERSAL AND RECRUITMENT LIMITATION ACROSS SPATIAL SCALES IN TEMPERATE FOREST FRAGMENTS

Despite increasing evidence of seed limitation in forest ecosystems, data remain sparse on spatial patterns of seed rain at large (>1 ha) spatial scales. We monitored seed rain (28.5 m2) throughout five northern hardwood forest fragments (27 ha sampled across 14-km2 area) in southeastern Michigan over two years. Four fragments were nearest neighbors (300–700 m), yet varied in species composition, providing the opportunity to detect landscape-scale seed exchange. Of the 37 species of woody plants present in the seed rain (98 032 mature seeds), only three (Betula papyrifera, Ostrya virginiana, and Ulmus americana) had widespread seed dispersions within all fragments containing resident sources (seed in >70% of traps in each fragment). Seed dispersions, measured as the percentage of traps within a fragment receiving seed, differed among species using different dispersal vectors with animal-dispersed species arriving in a lower percentage of seed traps than wind-dispersed seeds. At a given source density, seed dispersions increased with decreasing seed mass. Light-seeded, fecund species such as Betula or Tsuga required lower source densities to saturate fragments with seed compared to heavy-seeded species (Acer, Fraxinus, Tilia). Heavy-seeded wind- and animal-dispersed species also displayed the strongest evidence of seed limitation, with seedling presence significantly associated with presence of seed for Carpinus caroliniana, Fagus grandifolia, Prunus avium, and Tilia americana. Of 17 species, landscape-scale seed exchange was detected for only four disturbance-associated species (Acer negundo, Betula papyrifera, Celastrus scandens, Eleaganus umbellata). No exchange was detected for Acer rubrum, Betula alleghaniensis, or Tsuga canadensis, despite broad seed dispersions (>50%) in fragments with resident sources, suggesting the potential for seed limitation for these species at larger spatial scales. Seed encounter probabilities suggest that potential seed competitors often fail to simultaneously colonize microsites. We suggest that all dominant species in northern hardwood forests can be seed limited at some spatial scale and that results are consistent with “winning by forfeit” scenarios of diversity maintenance in forest ecosystems.

EFFECTS OF SMALL RODENTS AND LARGE MAMMALS ON NEOTROPICAL SEEDS

The direct and indirect effects of seed predation by a Neotropical community of small rodents and large mammals were examined in a 1.5-year exclosure experiment in Corcovado National Park, Costa Rica. This park has an intact terrestrial mammalian community, including small rodents and large mammalian seed predators, an essential condition to quantify the dynamics of seed predation. To measure seed predation, three exclosure treatments (1.2 m radius × 1.5 m tall) in two forest types (primary vs. secondary forest) were monitored: (1) fenced exclosures that excluded large mammals, (2) fenced exclosures that excluded both large and small mammals, and (3) open controls. Tethered seeds were added from nine common species of canopy trees and lianas (seven families), and seed removal was measured from February 2001 to July 2002. Small rodents had significant negative effects on four of the nine seed species tested, and the effects of small rodents on seed predation differed significantly from the effects of large mammals and insect/fungal pathogens. Small-rodent seed predation (both rates and total proportion destroyed) did not differ between secondary and primary forest habitats. Throughout the exclosure study, small-rodent populations were marked and recaptured to document their community composition and densities. Small-rodent population fluctuations were observed, and shifts in composition directly affected species-specific and community-wide seed predation. Fewer seeds were destroyed when small-rodent abundance was low. Small-rodent population fluctuations also had an indirect effect, reversing the relative importance of small rodents and large mammals and resulting in large mammals becoming the primary seed predators. This change did not only decrease total seed predation for some species; it had the additional effect of moving from a primarily negative interaction (seed predation from the small rodents) to the varied interactions of seed predation and seed dispersal (scatter-hoarding). This research illustrated that small-rodent community fluctuations are a mechanism responsible for variability in the process of Neotropical seedling regeneration.

Multiple Pathways of Commodity Crop Expansion in Tropical Forest Landscapes

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.

Understanding the Impacts of Land-Use Policies on a Threatened Species: Is There a Future for the Bornean Orang-utan?

The geographic distribution of Bornean orang-utans and its overlap with existing land-use categories (protected areas, logging and plantation concessions) is a necessary foundation to prioritize conservation planning. Based on an extensive orang-utan survey dataset and a number of environmental variables, we modelled an orang-utan distribution map. The modelled orang-utan distribution map covers 155,106 km2 (21% of Borneos landmass) and reveals four distinct distribution areas. The most important environmental predictors are annual rainfall and land cover. The overlap of the orang-utan distribution with land-use categories reveals that only 22% of the distribution lies in protected areas, but that 29% lies in natural forest concessions. A further 19% and 6% occurs in largely undeveloped oil palm and tree plantation concessions, respectively. The remaining 24% of the orang-utan distribution range occurs outside of protected areas and outside of concessions. An estimated 49% of the orang-utan distribution will be lost if all forest outside of protected areas and logging concessions is lost. To avoid this potential decline plantation development in orang-utan habitats must be halted because it infringes on national laws of species protection. Further growth of the plantation sector should be achieved through increasing yields in existing plantations and expansion of new plantations into areas that have already been deforested. To reach this goal a large scale island-wide land-use masterplan is needed that clarifies which possible land uses and managements are allowed in the landscape and provides new standardized strategic conservation policies. Such a process should make much better use of non-market values of ecosystem services of forests such as water provision, flood control, carbon sequestration, and sources of livelihood for rural communities. Presently land use planning is more driven by vested interests and direct and immediate economic gains, rather than by approaches that take into consideration social equity and environmental sustainability.

PHOSPHORUS EFFICIENCY OF BORNEAN RAIN FOREST PRODUCTIVITY: EVIDENCE AGAINST THE UNIMODAL EFFICIENCY HYPOTHESIS

Plant communities on nutrient-poor soils are thought to use nutrients more efficiently to produce biomass than plant communities on nutrient-rich soils. Yet, increased efficiency with declining soil nutrients has not been demonstrated empirically in lowland tropical rain forests, where plant growth is thought to be strongly limited by soil nutrients, especially phosphorus (P). We tested for higher P uptake and use efficiency across a 16-fold soil P gradient in lowland Borneo by measuring the P content of aboveground net primary productivity (fine litter production plus new tree growth; ANPP) for 24 months. Extractable soil P was positively related to litter production, tree growth, and ANPP. Efficiency of P response (ANPP/available soil P), uptake (P uptake/available soil P), and use (ANPP/P uptake) increased monotonically with declining soil P and was significantly higher on P-rich soil than P-poor soil. Increased P uptake and use efficiency with declining soil P enabled higher than expected plant produc...

Cenários de desmatamento para a Amazônia

A AMAZONIA esta entrando em uma era de rapidas mudancas impulsionadas pela previsao de asfaltamento de rodovias que estimularao a expansao da fronteira agricola e de exploracao madeireira. O declinio do custo de transporte tem importantes implicacoes para a biodiversidade, emissao de gases que contribuem para o efeito estufa e prosperidade da sociedade da Amazonia a longo prazo. Para analisar esse contexto, foi desenvolvido um modelo de simulacao de desmatamento na bacia Amazonica, sensivel a diferentes cenarios de politicas publicas frente a expansao da infra-estrutura de transporte pela regiao. Resultados do modelo indicam que, dentro de um cenario pessimista, o desmatamento projetado pode eliminar, ate meados deste seculo, 40% dos atuais 5,4 milhoes de km2 de florestas da Amazonia, liberando o equivalente a 32 Pg (109 toneladas) de carbono para atmosfera. A modelagem de cenarios alternativos aponta que a expansao de uma rede de areas protegidas, efetivamente implementadas, poderia reduzir em ate 1/3 as perdas florestais projetadas. Contudo, outras medidas de conservacao sao ainda necessarias para se manter a integridade funcional das paisagens e bacias hidrograficas amazonicas. Atuais experimentos em conservacao florestal em propriedades privadas, mercados de servicos ambientais e zoneamento agro-ecologico devem ser refinados e multiplicados a fim de se buscar uma conservacao extensiva.

Tropical land-cover change alters biogeochemical inputs to ecosystems in a Mexican montane landscape

In tropical regions, the effects of land-cover change on nutrient and pollutant inputs to ecosystems remain poorly documented and may be pronounced, especially in montane areas exposed to elevated atmospheric deposition. We examined atmospheric deposition and canopy interactions of sulfate-sulfur (SO4(2-)-S), chloride (Cl-), and nitrate-nitrogen (NO(3-)-N) in three extensive tropical montane land-cover types: clearings, forest, and coffee agroforest. Bulk and fog deposition to clearings was measured as well as throughfall (water that falls through plant canopies) ion fluxes in seven forest and five coffee sites. Sampling was conducted from 2005 to 2008 across two regions in the Sierra Madre Oriental, Veracruz, Mexico. Annual throughfall fluxes to forest and coffee sites ranged over 6-27 kg SO4(2-)-S/ha, 12-69 kg Cl-/ha, and 2-6 kg NO(3-)-N/ha. Sulfate-S in forest and coffee throughfall was higher or similar to bulk S deposition measured in clearings. Throughfall Cl- inputs, however, were consistently higher than Cl- amounts deposited to cleared areas, with net Cl- fluxes enhanced in evergreen coffee relative to semi-deciduous forest plots. Compared to bulk nitrate-N deposition, forest and coffee canopies retained 1-4 kg NO(3-)-N/ha annually, reducing NO(3-)-N inputs to soils. Overall, throughfall fluxes were similar to values reported for Neotropical sites influenced by anthropogenic emissions, while bulk S and N deposition were nine- and eightfold greater, respectively, than background wet deposition rates for remote tropical areas. Our results demonstrate that land-cover type significantly alters the magnitude and spatial distribution of atmospheric inputs to tropical ecosystems, primarily through canopy-induced changes in fog and dry deposition. However, we found that land cover interacts with topography and climate in significant ways to produce spatially heterogeneous patterns of anion fluxes, and that these factors can converge to create deposition hotspots. For land managers, this finding suggests that there is potential to identify species and ecosystems at risk of excess and increasing deposition in montane watersheds undergoing rapid transformation. Our data further indicate that montane ecosystems are vulnerable to air pollution impacts in this and similar tropical regions downwind of urban, industrial, and agricultural emission sources.

Seed-feeding beetles of the weevil tribe Mecysolobini (Insecta: Coleoptera: Curculionidae) developing in seeds of trees in the Dipterocarpaceae

Species comprising two monophyletic groups of Alcidodes sensu lato (crassus group and dipterocarpi group) feed on fruits of the ecologically and economically important tropical timber family Dipterocarpaceae. Fifteen Alcidodes species are newly described from several thousand specimens of seed-feeding beetles reared from south-east Asian dipterocarp hosts (Dipterocarpoidae) and four other species are revised. Morphological keys are provided for identifying these 19 taxa. Weevil associations are provided for 70 species of Dipterocarpaceae in five genera (16 Dipterocarpus spp., four Dryobalanops spp., six Hopea spp., 39 Shorea spp. and five Vatica spp.). These records relate primarily to specimens reared from seeds in Borneo and in Peninsular Malaysia, but all known previous host records are also included (from India, Andaman Islands, Thailand, Laos, Vietnam and the Philippines) and assessed. These validated and documented host associations refute general assertions that (1) seed-eating beetles are host-specific in the tropics and (2) seed-eating beetles found on dipterocarp hosts are broad generalists across species in several genera of mast-fruiting Dipterocarpaceae. Most Alcidodes species exploit seeds from several dipterocarp species. Some Alcidodes species occur across broad geographic regions with several host species from a dipterocarp genus, other species have been found only on Bornean Hopea or Dipterocarpus species. Others, such as the two previously undescribed species feeding on Vatica species, may be restricted to separate sections of the host genus. Within an extensively sampled and diverse interspecific mast-fruiting dipterocarp community, no Alcidodes species was observed to feed on sympatric species across genera within the Dipterocarpaceae. Additional host records and specimens of Alcidodes spp. throughout the range of the Dipterocarpaceae in south and southeast Asia are required to further define these clades and the tribe Mecysolobini in general as well as to resolve the complex host associations and distributions documented.