Eben N. Broadbent

Condition and fate of logged forests in the Brazilian Amazon

The long-term viability of a forest industry in the Amazon region of Brazil depends on the maintenance of adequate timber volume and growth in healthy forests. Using extensive high-resolution satellite analyses, we studied the forest damage caused by recent logging operations and the likelihood that logged forests would be cleared within 4 years after timber harvest. Across 2,030,637 km2 of the Brazilian Amazon from 1999 to 2004, at least 76% of all harvest practices resulted in high levels of canopy damage sufficient to leave forests susceptible to drought and fire. We found that 16 ± 1% of selectively logged areas were deforested within 1 year of logging, with a subsequent annual deforestation rate of 5.4% for 4 years after timber harvests. Nearly all logging occurred within 25 km of main roads, and within that area, the probability of deforestation for a logged forest was up to four times greater than for unlogged forests. In combination, our results show that logging in the Brazilian Amazon is dominated by highly damaging operations, often followed rapidly by deforestation decades before forests can recover sufficiently to produce timber for a second harvest. Under the management regimes in effect at the time of our study in the Brazilian Amazon, selective logging would not be sustained.

Biomass resilience of Neotropical secondary forests

Land-use change occurs nowhere more rapidly than in the tropics, where the imbalance between deforestation and forest regrowth has large consequences for the global carbon cycle. However, considerable uncertainty remains about the rate of biomass recovery in secondary forests, and how these rates are influenced by climate, landscape, and prior land use. Here we analyse aboveground biomass recovery during secondary succession in 45 forest sites and about 1,500 forest plots covering the major environmental gradients in the Neotropics. The studied secondary forests are highly productive and resilient. Aboveground biomass recovery after 20 years was on average 122 megagrams per hectare (Mg ha−1), corresponding to a net carbon uptake of 3.05 Mg C ha−1 yr−1, 11 times the uptake rate of old-growth forests. Aboveground biomass stocks took a median time of 66 years to recover to 90% of old-growth values. Aboveground biomass recovery after 20 years varied 11.3-fold (from 20 to 225 Mg ha−1) across sites, and this recovery increased with water availability (higher local rainfall and lower climatic water deficit). We present a biomass recovery map of Latin America, which illustrates geographical and climatic variation in carbon sequestration potential during forest regrowth. The map will support policies to minimize forest loss in areas where biomass resilience is naturally low (such as seasonally dry forest regions) and promote forest regeneration and restoration in humid tropical lowland areas with high biomass resilience.

Carbon sequestration potential of second-growth forest regeneration in the Latin American tropics

Models reveal the high carbon mitigation potential of tropical forest regeneration. Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km2 of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.

Social and environmental effects of ecotourism in the Osa Peninsula of Costa Rica: the Lapa Rios case

Ecotourism comes with a definitional promise to promote responsible travel to natural areas, to make a positive contribution to environmental conservation, and to enhance the well-being of local communities. This article summarises a study designed to test whether the Lapa Rios Eco-lodge of the Osa Peninsula of Costa Rica, a widely acclaimed example of the species, delivers on these promises and to what degree. The study uses an interdisciplinary nested-scale analysis, combining careful on-the-ground interview methods with remote sensing analysis of forest and land-use impact of the Lapa Rios (LR) lodge. This combination of methods allows us to reject the null hypothesis, confirming that LR lodge has made substantial contributions to both local livelihoods and environmental conservation, including the highest rates of reforestation of all areas studied in the Osa Peninsula. We conclude that LR fulfils the definitional promise of ecotourism and delivers social, economic, and environmental benefits in the region.

The effect of land use change and ecotourism on biodiversity: a case study of Manuel Antonio, Costa Rica, from 1985 to 2008

Development in biodiversity rich areas is of global concern. While development may lead to socioeconomic benefits, this often comes concomitant with biodiversity loss and deforestation. Biodiversity rich areas present the opportunity for both improvements in socioeconomic conditions and conservation; however numerous challenges exist. Costa Rica’s Manuel Antonio National Park presents an ideal case study to investigate the balance between alternative forms of development which have contrasting environmental impacts. The Manuel Antonio region is a highly dynamic landscape experiencing deforestation, from agriculture, cattle ranching and oil palm plantations; and also reforestation from abandonment of land holdings and nature oriented tourism. Landscape dynamics are closely intertwined with the livelihoods and perspectives on biodiversity conservation of local communities, determining ecological sustainability. We use an analysis combining multi-temporal remote sensing of land cover dynamics from 1985 to 2008 with questionnaire data from local families on their socioeconomic status, perspectives on conservation, and perceived changes in local wildlife populations. Our results show that, while regeneration occurred and forest fragmentation in the area decreased from 1985 to 2008, Manuel Antonio National Park is rapidly becoming isolated. Decreasing ecological connectivity is related to the rapid expansion of oil palm plantations adjacent to the park and throughout the lowland areas. Perceived decreases in wildlife abundance and compositional change are evident throughout the area, with local communities attributing this primarily to illegal hunting activities. Nature based tourism in the area presents an effective strategy for conservation, including reductions in hunting, through increased valuation of biodiversity and protected areas, and socioeconomic advantages. However, without urgent efforts to limit deforestation and preserve the remaining forested corridor connecting the park to core primary forest, the ability to maintain biodiversity in the park will be reduced.

Recovery Of Forest Structure And Spectral Properties After Selective Logging In Lowland Bolivia

Effective monitoring of selective logging from remotely sensed data requires an understanding of the spatial and temporal thresholds that constrain the utility of those data, as well as the structural and ecological characteristics of forest disturbances that are responsible for those constraints. Here we assess those thresholds and characteristics within the context of selective logging in the Bolivian Amazon. Our study combined field measurements of the spatial and temporal dynamics of felling gaps and skid trails ranging from <1 to 19 months following reduced-impact logging in a forest in lowland Bolivia with remote-sensing measurements from simultaneous monthly ASTER satellite overpasses. A probabilistic spectral mixture model (AutoMCU) was used to derive per-pixel fractional cover estimates of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil. Results were compared with the normalized difference in vegetation index (NDVI). The forest studied had considerably lower basal area and harvest volumes than logged sites in the Brazilian Amazon where similar remote-sensing analyses have been performed. Nonetheless, individual felling-gap area was positively correlated with canopy openness, percentage liana coverage, rates of vegetation regrowth, and height of remnant NPV. Both liana growth and NPV occurred primarily in the crown zone of the felling gap, whereas exposed soil was limited to the trunk zone of the gap. In felling gaps >400 m2, NDVI, and the PV and NPV fractions, were distinguishable from unlogged forest values for up to six months after logging; felling gaps <400 m2 were distinguishable for up to three months after harvest, but we were entirely unable to distinguish skid trails from our analysis of the spectral data.

Deforestation drivers in Southwest Amazonia: Comparing smallholder farmers in Iñapari, Peru, and Assis Brasil, Brazil

Broad interpretation of land use and forest cover studies has been limited by the biophysical and socio-economic uniqueness of the landscapes in which they are carried out and by the multiple temporal and spatial scales of the underlying processes. We coupled a land cover change approach with a political ecology framework to interpret trends in multi-temporal remote sensing of forest cover change and socio-economic surveys with smallholders in the towns of Inapari, Peru and Assis Brasil, Brazil in southwest Amazonia. These adjacent towns have similar biogeophysical conditions, but have undergone differing development approaches, and are both presently undergoing infrastructure development for the new Interoceanic highway. Results show that forest cover patterns observed in these two towns cannot be accounted for using single land use drivers. Rather, deforestation patterns result from interactions of national and regional policies affecting financial credit and road infrastructure, along with local processes of market integration and household resources. Based on our results we develop recommendations to minimise deforestation in the study area. Our findings are relevant for the sustainability of land use in the Amazon, in particular for regions undergoing large-scale infrastructure development projects.

Integrating Stand and Soil Properties to Understand Foliar Nutrient Dynamics during Forest Succession Following Slash-and-Burn Agriculture in the Bolivian Amazon

Secondary forests cover large areas of the tropics and play an important role in the global carbon cycle. During secondary forest succession, simultaneous changes occur among stand structural attributes, soil properties, and species composition. Most studies classify tree species into categories based on their regeneration requirements. We use a high-resolution secondary forest chronosequence to assign trees to a continuous gradient in species successional status assigned according to their distribution across the chronosequence. Species successional status, not stand age or differences in stand structure or soil properties, was found to be the best predictor of leaf trait variation. Foliar δ13C had a significant positive relationship with species successional status, indicating changes in foliar physiology related to growth and competitive strategy, but was not correlated with stand age, whereas soil δ13C dynamics were largely constrained by plant species composition. Foliar δ15N had a significant negative correlation with both stand age and species successional status, – most likely resulting from a large initial biomass-burning enrichment in soil 15N and 13C and not closure of the nitrogen cycle. Foliar %C was neither correlated with stand age nor species successional status but was found to display significant phylogenetic signal. Results from this study are relevant to understanding the dynamics of tree species growth and competition during forest succession and highlight possibilities of, and potentially confounding signals affecting, the utility of leaf traits to understand community and species dynamics during secondary forest succession.

Linking rainforest ecophysiology and microclimate through fusion of airborne LiDAR and hyperspectral imagery

We develop and validate a high-resolution three-dimensional model of light and air temperature for a tropical forest interior in Hawaii along an elevation gradient varying greatly in structure but maintaining a consistent species composition. Our microclimate models integrate high-resolution airborne waveform light detection and ranging data (LiDAR) and hyperspectral imagery with detailed microclimate measurements. We then use modeled microclimate and forest structural and compositional variables to explain variation in spatially explicit measurements of leaf traits, including gas exchange and structure. Our results highlight the importance of: (1) species differences in leaf traits, with species explaining up to 65% of the variation in some leaf traits; (2) differences between exotic and native species, with exotic species having greater maximum rates of assimilation and foliar δ15N values; (3) structural factors, with foliar %N and light saturation of photosynthesis decreasing in mid-canopy locations; (4) microclimate factors, with foliar %N and light saturation increasing with growth environment illumination; and (5) decreases in mean annual temperature with elevation resulting in closure of the nitrogen cycle, as indicated through decreases in foliar δ15N values. The dominant overstory species (Metrosideros polymorpha) did not show plasticity in photosynthetic capacity, whereas the dominant understory species (Cibotium glaucum) had higher maximum rates of assimilation in more illuminated growth environments. The approach developed in this study highlights the potential of new airborne sensors to quantify forest productivity at spatial and temporal scales not previously possible. Our results provide insight into the function of a Hawaiian forest dominated by native species undergoing simultaneous biological invasion and climatic change.