Tropical Contexts Research Articles

The Prevalence of Marine Lipophilic Phycotoxins Causes Potential Risks in a Tropical Small Island Developing State.

Tropical small island developing states (SIDS), with their geographical isolation and limited resources, heavily rely on the fisheries industry for food and revenue. The presence of marine lipophilic phycotoxins (MLPs) poses risks to their economy and human health. To understand the contamination status and potential risks, the Republic of Kiribati was selected as the representative tropical SIDS and 55 species of 256 coral reef fish encompassing multiple trophic levels and feeding strategies were collected to analyze 17 typical MLPs. Our results showed that the potential risks of ciguatoxins were the highest and approximately 62% of fish species may pose risks for consumers. Biomagnification of ciguatoxins was observed in the food web with a trophic magnification factor of 2.90. Brevetoxin-3, okadaic acid, and dinophysistoxin-1 and -2 were first reported, but the risks posed by okadaic acid and dinophysistoxins were found to be negligible. The correlation analysis revealed that fish body size and trophic position are unreliable metrics to indicate the associated risks and prevent the consumption of contaminated fish. The potential risks of MLPs in Kiribati are of concern, and our findings can serve as valuable inputs for developing food safety policies and fisheries management strategies specific to tropical SIDS contexts.

Vertical Greenery Systems in Tropical Climate - A Review

In burgeoning tropical urban areas, impermeable surfaces exacerbate urban heat stress, creating Urban Heat Islands (UHI). Mitigating this requires the adaptation of Vertical Greenery Systems (VGS) in the built environment. While studies explore VGS, few address their environmental impact in tropical contexts, where adverse weather challenges the design and management. Guided by 'Green wall,' this study categorizes literature on VGS into systems, technical properties, and tropical challenges. Scrutinizing climate, maintenance, and cost as barriers, the study aims to identify factors influencing successful VGS deployment in the tropics. Objectives include exploring typologies, designs, performances, irrigation, maintenance challenges, and climatic factors. Insights seek to offer a nuanced understanding of their efficacy across climates. Recommendations stress the need for targeted tropical research, a multidisciplinary maintenance approach, meticulous material selection, and ongoing technological adaptation for sustainable VGS in tropical urban landscapes.

Modeling of soil erosion risk in a typical tropical savannah landscape

Tropical savannah landscapes are faced with high soil degradation due to climate change and variability coupled with anthropogenic factors. However, the spatiotemporal dynamics of this is not sufficiently understood particularly, in the tropical savannah contexts. Using the Wa municipality of Ghana as a case, we applied the Revised Universal Soil Loss Equation (RUSLE) model to predict the potential and actual soil erosion risk for 1990 and 2020. Rainfall, soil, topography and land cover data were used as the input parameters. The rate of predicted potential erosion was in the range of 0–111 t ha−1yr−1 and 0–83 t ha−1yr−1 for the years 1990 and 2020, respectively. The prediction for the rate of potential soil erosion risk was generally higher than the actual estimated soil erosion risk which ranges from 0 to 59 t ha−1yr−1 in 1990 and 0 to 58 t ha−1yr−1 in 2020. The open savannah areas accounted for 75.8 % and 73.2 % of the total soil loss in 1990 and 2020, respectively. The validity of the result was tested using in situ data from a 2 km2 each of closed savannah, open savannah and settlement area. By statistical correlation, the predicted soil erosion risk by the model corresponds to the spatial extent of erosion damages measured in the selected area for the validation. Primarily, areas with steep slopes, particularly within settlement, were identified to have the highest erosion risk. These findings underscore the importance of vegetation cover and effective management practices in preventing soil erosion. The results are useful for inferences towards the development and implementation of sustainable soil conservation practice in landscapes with similar attributes.

Bone collagen from subtropical Australia is preserved for more than 50,000 years

Ancient protein studies have demonstrated their utility for looking at a wide range of evolutionary and historical questions. The majority of palaeoproteomics studies to date have been restricted to high latitudes with relatively temperate environments. A better understanding of protein preservation at lower latitudes is critical for disentangling the mechanisms involved in the deep-time survival of ancient proteins, and for broadening the geographical applicability of palaeoproteomics. In this study, we aim to assess the level of collagen preservation in the Australian fossil record. Collagen preservation was systematically examined using a combination of thermal age estimates, Fourier Transform Infrared Spectroscopy, Zooarchaeology by Mass Spectrometry, and protein deamidation calculations. We reveal unexpected subtropical survival of collagen in bones more than 50 thousand years old, showing that protein preservation can exceed chemical predictions of collagen survival in bone. These findings challenge preconceptions concerning the suitability of palaeoproteomics in subtropical Pleistocene environments. We explore potential causes of this unexpected result to identify the underlying mechanisms leading to this exceptional preservation. This study serves as a starting point for the analysis of ancient proteins in other (sub)tropical contexts, and at deeper timescales.

Association between heavy metal uptake and growth and reproduction in the anecic earthworm, Alma nilotica (Grube 1855).

Elevated heavy metal concentrations in soils are a cause for concern as they are hazardous to soil organisms including earthworms which are considered as ecosystem engineers. Current ecotoxicity tests predominantly use temperate earthworm species, and thus there is the need to include a broader genera of native species to improve ecological risk assessment. Alma nilotica, is a tropical anecic earthworm species that survives well under laboratory conditions and has potential for use in ecotoxicology testing but lacks published toxicity data for important pollutants. Growth and reproduction bioassays were carried out with A. nilotica to determine the relationship between the concentrations of Cu, Zn, Pb and Cr in spiked soils and their bioaccumulation and toxic effects. Positive linear relationships were found between soil-metal and internal earthworm-metal concentrations. Cu did not inhibit growth up to 35 days of exposure but became toxic with longer exposure duration. Zn was not regulated by A. nilotica although it is an essential metal that is well regulated by Eisenia sp. commonly used in standard ecotoxicity tests, showing differences in metal regulation by earthworms of different ecological categories. Based on bioaccumulation factors (BAFs), growth inhibition and reproduction effects the metals were ranked in decreasing toxicity as Pb > Cr > Zn > Cu. The mean 20% Internal Effects Concentrations (IEC20s) for reproduction were 1.04, 2.9, 8.3 and 224.2 mg metal kg-1 earthworm for Pb, Cr, Zn and Cu respectively. These data can contribute to the improvement of metal risk assessment particularly in tropical contexts.

Households' livelihood in restricted forest landscapes: What is the impact of contextual factors?

In response to the loss of forest cover and biodiversity, forest conservation policies have been increasingly pursued worldwide. Such policies are often criticized for limiting the access of locals to forest resources, raising the question if nature conservation and poverty alleviation goals are compatible. Few studies have attempted to examine the impact of forest restriction on the livelihood of neighboring communities by accounting for confounding factors. We address this gap by estimating the impact of contextual factors in the wider landscape as well as forest legal restrictions on households' main income sources. The current study relies on a comprehensive dataset from 3410 households living in different tropical contexts in forested landscapes of Zambia, Ecuador and the Philippines. We adopt a multi-level regression model by including explanatory variables at both household and landscape levels. Our results indicate the significance of the broader landscape's context such as elevation, road access and extent of remaining forest for households' income. Country context is particularly important in determining households' income. Households' characteristics and asset endowment play a major role too. Our findings provide no evidence that increasing restricted forest extent in landscape decreases households' income when contextual factors are controlled for. This study highlights the non-random designation of forest conservation policies, with many conservation programs being assigned to areas with little development potential. Thus, we argue that contextual factors in which households function shall be given more attention in the debate of nature protection versus poverty reduction. Suggesting the insignificant impact of forest conservation policies on households' livelihoods, our findings serve to inform policymakers in establishing effectual forest conservation policies which strike the right balance between nature protection and rural development.

Flow patterns and pathways of legacy and contemporary pesticides in surface waters in tropical volcanic catchments

Severe water pollution issues due to legacy and contemporary pesticides exist in tropical regions and are linked to cash crops requiring intensive plant protection practices. This study aims to improve knowledge about contamination routes and patterns in tropical volcanic settings to identify mitigation measures and analyse risk. To this aim, this paper analyses four years of monitoring data from 2016 to 2019 of flow discharge and weekly pesticide concentrations in the rivers of two catchments grown predominantly with banana and sugar cane in the French West Indies. The banned insecticide chlordecone, applied in banana fields from 1972 to 1993, was still the major source of river contamination, while the currently used herbicide glyphosate, its metabolite aminomethylphosphonic acid (AMPA), and postharvest fungicides also exhibited high contamination levels. A value of 0.5 of the Gustafson Ubiquity Score (GUS) was shown to separate contaminant and noncontaminant pesticides, indicating a high vulnerability to pollution by pesticides in this tropical volcanic context. The patterns and routes of river exposure to pesticides differed markedly between the pesticides in accordance with the hydrological behaviour of volcanic islands and the history and nature of pesticide uses. Concerning chlordecone and its metabolites, observations confirmed previous findings of a main subsurface origin of river contamination by this compound but also showed large erratic short-term variations, suggesting the influence of fast surface transport processes such as erosion for legacy pesticides with large sorption capacity. Concerning herbicides and postharvest fungicides, observations have suggested that surface runoff and fast lateral flow in the vadose zone control river contamination. Accordingly, mitigation options need to be considered differently for each type of pesticide. Finally, this study points out the need for developing specific exposure scenarios for tropical agricultural contexts in the European regulation procedures for pesticide risk assessment.

Hydropower Hegemony: Examining Civil Society Opposition to Dams in Cambodia

As the urgency of addressing the climate crisis gathers pace, the role of hydropower is likely to attract increased interest for its claimed sustainability, despite fragmenting fragile river systems and evidence of significant emissions when constructed in tropical contexts. Building upon existing post-development, political ecology and civil society literature, this paper examines civil society opposition to hydropower projects in Cambodia. The paper introduces the term ‘hydropower hegemony,’ as an analytical tool for examining not just the tactical dimensions of civil society opposition to hydropower, but also the importance of ideological contestation. This analysis is applied to two case studies, Lower Sesan 2 and the Areng Valley in Cambodia, but with relevance for populations in peripheral areas and countries facing the expansion of hydropower projects. The case studies illustrate a spectrum of approaches to contestation, from reform to confrontation, and their intersections with the rapacious Cambodian state. The analysis also challenges reductionist characterizations of civil society in Cambodia. Despite the presence and success of confrontation with the state, we suggest that civil society’s increasingly reformist approaches are ultimately reinforcing hegemony, hydropower and otherwise, rather than challenging it, by inadvertently taming and domesticating burgeoning opposition to dispossession.

Seismic and geomorphic assessment for coseismic landslides zonation in tropical volcanic contexts

The Poás volcano is an active volcano of Costa Rica with intense tectonic activity in its flanks. Historically, the volcano has presented strong, surficial earthquakes provoking many landslides with associated casualties and immense economic impacts. One example is the Cinchona earthquake in 2009 (Mw 6.2 and 4.6 km depth). We aim to determine a landslide zonation according to seismic data and a geomorphic assessment in the NW sector of the Poás volcano based on a combination of qualitative methods and morphometric parameters. The results estimate the possible outcome of a 6.8 Mw earthquake. The susceptibility mapping and models showed a positive relationship between this methodology and others previously developed for the area that surrounds the Poás volcano as well as a correspondence with the landslides caused by the Cinchona earthquake in 2009. The final coseismic landslides susceptibility zoning indicated that 52% of the area is prone to landslides. Furthermore, there is a relationship between the areas with high exposure to landslides with conical volcanic geomorphologies, active faulting structural and/or tectonic geomorphological units with slopes greater than 15°. The proposed zoning can be useful for land use planning and by civil protection entities to orientate quick response and reduce the impact of future landslides. Moreover, this method can be applied in active tectonic and volcanic areas worldwide.

Effects of replacing Brachiaria hay with either Desmodium intortum or dairy concentrate on animal performance and enteric methane emissions of low-yielding dairy cows

In Africa, cattle are often fed low quality tropical roughages resulting in low-yielding animals with high methane (CH4) emission intensity (EI, g CH4/per unit of product). Supplementation with protein is known to improve the nutritive value of the otherwise low-quality diets. However, animal nutrition studies in East Africa that are accompanied by CH4 emission measurements are lacking. Thus, an animal experiment was conducted to quantify the effect of supplementing cattle fed mainly on low-quality Urochloa brizantha hay (control diet; CON; crude protein (CP) = 7.4%) or supplemented with either a tannin-rich leguminous fodder, Desmodium intortum hay (DES) or a commercial dairy concentrate (CUBES) on voluntary dry matter intake (DMI), nutrient apparent total tract digestibility, nitrogen (N) retention, enteric CH4 production and animal performance (milk and average daily gain). Twelve mid-lactating crossbred (Friesian × Boran) cows (initial liveweight = 335 kg) were used in a 3×3 (Period × Diet) Latin square design with each period running for four weeks. Compared to CON, DES decreased nutrient (DM, OM, CP) intake, apparent total tract digestibility and daily milk yield. In contrast, CUBES increased nutrient intake and animal performance compared to CON, while nutrients’ apparent total tract digestibility was not different, except for CP digestibility that increased. Compared to CON, DES and CUBES improved overall N retention by the animals as a proportion of N intake. The DES diet compared with CON and CUBES, shifted the proportion of N excretion via urine to the fecal route, likely because of its tannin content. Both DES and CUBES, compared to CON, reduced methane yield (MY, g CH4/kg DMI) by 15% and 9%, respectively. The DES diet reduced absolute enteric CH4 emissions by 26% while CUBES increased emissions by 11% compared to CON. Based on the present findings, high supplementation levels (>50%) of Desmodium intortum hay is not recommended especially when the basal diet is low in CP content. Supplementation with lower levels of better managed Desmodium intortum forage however, need to be investigated to establish optimal inclusion levels that will improve animal productivity and reduce environmental impact of livestock in smallholder tropical contexts.

Impact of delayed processing of positive blood cultures on organism detection: a prospective multi-centre study

BackgroundBlood cultures remain the gold standard investigation for the diagnosis of bloodstream infections. In many locations, quality-assured processing of positive blood cultures is not possible. One solution is to incubate blood cultures locally, and then transport bottles that flag positive to a central reference laboratory for organism identification and antimicrobial susceptibility testing. However, the impact of delay between the bottle flagging positive and subsequent sub-culture on the viability of the isolate has received little attention.MethodsThis study evaluated the impact of delays to sub-culture (22 h to seven days) in three different temperature conditions (2–8 °C, 22–27 °C and 35 ± 2 °C) for bottles that had flagged positive in automated detection systems using a mixture of spiked and routine clinical specimens. Ninety spiked samples for five common bacterial causes of sepsis (Escherichia coli, Haemophilus influenzae, Staphylococcus aureus, Streptococcus agalactiae and Streptococcus pneumoniae) and 125 consecutive positive clinical blood cultures were evaluated at four laboratories located in Cambodia, Lao PDR and Thailand. In addition, the utility of transport swabs for preserving organism viability was investigated.ResultsAll organisms were recoverable from all sub-cultures in all temperature conditions with the exception of S. pneumoniae, which was less likely to be recoverable after longer delays (> 46–50 h), when stored in hotter temperatures (35 °C), and from BacT/ALERT when compared with BACTEC blood culture bottles. Storage of positive blood culture bottles in cooler temperatures (22–27 °C or below) and the use of Amies bacterial transport swabs helped preserve viability of S. pneumoniae.ConclusionsThese results have practical implications for the optimal workflow for blood culture bottles that have flagged positive in automated detection systems located remotely from a central processing laboratory, particularly in tropical resource-constrained contexts.

Standard for School Design in The Tropics: Compliance and Classroom Comfort

For the design of schools in Colombia, NTC 4595: Planning and Design of School Facilities and Environments, offers design recommendations to achieve comfortable spaces in terms of thermal, visual and auditory comfort. The aim of the contribution, derived from a PhD research, is to analyze the comfort in classrooms of public schools in Cali in terms of: a. climatic moments and b. level of compliance with the Technical Standard, in order to validate the relevance of the recommendations to the comfort perceived by students. The methodology used is the User Perception Environmental Audit, in four public schools, for which measurements of environmental parameters were made with specialized equipment and surveys of 535 students. Statistical processing was carried out using test for paired samples, and one way ANOVA's. Among the main findings is the low use of external environmental conditions, derived from inflexible architectural envelopes; in addition to the low relationship between compliance with the standard and the comfort perceived by students. This demonstrates the need for further study of the normative ranges and recommendations for tropical contexts such as the one studied.

Forest plantations and local economic development: Evidence from Minas Gerais, Brazil

Globally, Brazil is one of the most important producers of wood products from forest plantations. Climatic conditions suitable for high productivity coupled with strong market demand and other factors have led to a marked increase in the area devoted to forest plantations in the country. Wood production from these plantations has brought important macroeconomic benefits through export. However, knowledge of the socio-economic impacts of forest plantations at sub-national levels remains limited in Brazil as in other tropical country contexts. This study addresses this knowledge gap by analyzing the socioeconomic impacts of forest plantations across the municipalities of Minas Gerais, the state with the largest plantation area in Brazil since 1980. We use panel data regression methods to analyze the relationship between forest plantation area, poverty, and other variables over a 20-year period. The results show that an increase in forest plantation area is associated with a decrease in poverty over time. Our findings run counter to much of the current evidence on the socio-economic impacts of forest plantations and have important implications for research and policy on this topic not only in Brazil, but elsewhere in Latin America and beyond.

Economic valuation of water services related to protected forest management: a case of Bukit Batabuh in the RIMBA corridor, Central Sumatra, Indonesia

The context of daily household needs of rural communities, particularly the needs for water, often remains insufficiently considered in tropical forest management as it is facing an important decision-making trade-off between profit and preservation. We conducted a choice experiment study to elicit preferences of the rural community members in Central Sumatra, Indonesia, who perpetually depend on the ecosystem services of tropical forests. To inform a spatial planning policy for the protected forest, we focus on the valuation of water services in the protected forest area of Bukit Batabuh where the surrounding communities living rely on upstream watershed and water storage management. We find that those communities have a strict preference for improving forest water provisioning services, compared to the current situation (status quo), with the estimated aggregate benefit of non-commercial use ranging between USD 2.71 million and USD 2.47 million per year for each of the options of (1) maintaining and enhancing water storage, (2) rehabilitating forest in the upper watershed or (3) restoring the riparian forest. This study also identifies preference attributes, such as water storage capacity, water scarcity and water turbidity which can be used in other tropical landscape contexts in Indonesia and beyond.

Passive cooling design strategies as adaptation measures for lowering the indoor overheating risk in tropical climates

Year-round high temperatures and humidity in the Tropics, coupled with poor design decisions and climate change, can cause indoor environments to overheat, affecting health and increasing energy demand and carbon emissions. Passive cooling could help lower the indoor overheating risk. Given the gap in the relative influence of passive cooling design strategies on lowering the indoor overheating risk in tropical locations, this study investigated their impact in two warm tropical cities (i.e., Tegucigalpa and San Pedro Sula), considering both current and future climate scenarios, with a total of 3840 thermal simulations performed. Indoor overheating risk in apartment-type dwellings was assessed using two metrics (i.e., hours of exceedance and the indoor overheating degree), and considering fixed and adaptive thermal comfort limits. Simulation results show that the overheating risk can be significantly lowered in these tropical contexts using solely passive cooling strategies as heat adaptation measures. Multivariate regression models demonstrate that natural ventilation, wall absorptance, the solar heat gain coefficient, and semi-outdoor spaces have the greatest impact in lowering the risk in vertical social housing projects. This study emphasizes the importance of passive cooling and overheating protection design strategies in tropical building codes and building design while considering current and future risk.

A comprehensive calibration and validation of SWAT-T using local datasets, evapotranspiration and streamflow in a tropical montane cloud forest area with permeable substrate in central Veracruz, Mexico

Tropical montane cloud forests (TMCF) are threatened ecosystems despite their capacity to maintain high dry-season baseflow. A number of conservation policies, including payments for hydrological services, have been implemented to protect these forests. However, since most of the modeling tools used to assess the impacts of these policies were developed for temperate zones, more work is needed to understand and improve the applicability of popular models in tropical contexts. This study uses local evapotranspiration and streamflow datasets to calibrate and validate an improved version of the Soil and Water Assessment Tool model for the Tropics (SWAT-T). Vegetation growth and canopy water storage capacity were calibrated using field data. Three methods provided by SWAT-T to calculate potential evapotranspiration (PET) were compared: Penman-Monteith (SWAT-T-PM), Hargreaves (SWAT-T-HA), and Priestly-Taylor (SWAT-T-PT). Sensitivity analysis and calibration of daily streamflow were conducted at the catchment scale (34 km2). Furthermore, the calibrated models were validated at three sites with evapotranspiration data, and at four distinct micro-catchments (0.137–0.446 km2) with gauged streamflow data. Overall, SWAT-T satisfactorily simulated streamflow during the calibration period producing acceptable goodness of fit indices. However, the model incorrectly predicted the dominance of lateral flow instead of the deep groundwater flow observed from isotope-based studies. SWAT-T-HA performed better than SWAT-T-PM and SWAT-T-PT, but all models underestimated the influence of rainfall interception losses since evaporation is limited by daily PET in forests. Finally, SWAT-T largely over- and underestimated mean annual daily low flow in pastures and forests, respectively. Taken together, these results indicate that improvements in the parametrization of rainfall interception and deep subsurface flow dynamics in SWAT-T are required to improve applicability of this modeling tool in tropical montane areas underlain by permeable substrates.

Effects of Urbanization on Plant-Pollinator Interactions in the Tropics: An Experimental Approach Using Exotic Plants.

Simple SummaryIsland environments of the Southwest Pacific, like New Caledonia, generally present poorly diversified bee fauna. Thus, they are particularly prone to the establishment of introduced bee species. These exotic species may compete with native bees for plant resources, disrupt pollination of native plants, and enhance the reproduction of exotic ones. To conserve local plant–pollinator interactions, it is essential to assess the factors favoring the presence and the activity of exotic bees. Here, we focused on the effects of urbanization on plant–pollinator interactions. We set up experimental plant communities composed of four exotic species in two contrasted habitats—a natural environment vs. an urban environment—and observed plant–pollinator interactions. We showed that the urban environment was largely dominated by exotic bees. We also showed that some exotic bee species can interact preferentially with a single exotic ornamental plant species. Overall, our results indicate that Nouméa is an entry point for exotic bees, which should encourage local authorities to maintain biosecurity measures to effectively limit the arrival of exogenous bees. Lastly, the use of exotic horticultural plants in green public spaces should be questioned regarding their potential attractiveness to exotic bees.Land-use changes through urbanization and biological invasions both threaten plant-pollinator networks. Urban areas host modified bee communities and are characterized by high proportions of exotic plants. Exotic species, either animals or plants, may compete with native species and disrupt plant–pollinator interactions. These threats are heightened in insular systems of the Southwest Pacific, where the bee fauna is generally poor and ecological networks are simplified. However, the impacts of these factors have seldom been studied in tropical contexts. To explore those questions, we installed experimental exotic plant communities in urban and natural contexts in New Caledonia, a plant diversity hotspot. For four weeks, we observed plant–pollinator interactions between local pollinators and our experimental exotic plant communities. We found a significantly higher foraging activity of exotic wild bees within the city, together with a strong plant–pollinator association between two exotic species. However, contrary to our expectations, the landscape context (urban vs. natural) had no effect on the activity of native bees. These results raise issues concerning how species introduced in plant–pollinator networks will impact the reproductive success of both native and exotic plants. Furthermore, the urban system could act as a springboard for alien species to disperse in natural systems and even invade them, leading to conservation concerns.

Environmental justice in urban greening for subtropical Asian cities: the view from Taipei

Whilst an extensive body of literature exists on the environmental justice implications of urban greening in North America, Europe and to an extent Australasia, there are fewer analogous studies for tropical zone Asian city contexts. Given increasing global interest in the potential for urban greenspace to contribute to resilience in the face of environmental change and the higher vulnerability of Asian cities to environmental shocks, this is a notable gap. In response, this paper evaluates the contours of environmental justice debates within urban greenspace planning for one subtropical Asian city—Taipei. Through analysis of newspaper reporting on urban greenspace planning within Taipei, the potential and limitations of greenspace planning in contributing to equitably delivering benefits from urban greenspace towards resilience are assessed. Findings suggest that claims to environmental injustice in greenspace debates within Taipei follow broadly similar lines to controversies in Europe and North America. Nevertheless, the need for specific knowledge to understand the different ecosystem services provided by tropical zone ecosystems, and the potential for conflicts over greenspace versus development to be heightened in dense Asian city settings, are highlighted as potential areas where environmental justice debates in an Asian urban greening context may differ from Western cities.

Scale and context dependency of deforestation drivers: Insights from spatial econometrics in the tropics.

A better understanding of deforestation drivers across countries and spatial scales is a precondition for designing efficient international policies and coherent land use planning strategies such as REDD+. However, it is so far unclear if the well-studied drivers of tropical deforestation behave similarly across nested subnational jurisdictions, which is crucial for efficient policy implementation. We selected three countries in Africa, America and Asia, which present very different tropical contexts. Making use of spatial econometrics and a multi-level approach, we conducted a set of regressions comprising 3,035 administrative units from the three countries at micro-level, plus 361 and 49 at meso- and macro-level, respectively. We included forest cover as dependent variable and seven physio-geographic and socioeconomic indicators of well-known drivers of deforestation as explanatory variables. With this, we could provide a first set of highly significant econometric models of pantropical deforestation that consider subnational units. We identified recurrent drivers across countries and scales, namely population pressure and the natural condition of land suitability for crop production. The impacts of demography on forest cover were strikingly strong across contexts, suggesting clear limitations of sectoral policy. Our findings also revealed scale and context dependencies, such as an increased heterogeneity at local scopes, with a higher and more diverse number of significant determinants of forest cover. Additionally, we detected stronger spatial interactions at smaller levels, providing empirical evidence that certain deforestation forces occur independently of the existing de jure governance boundaries. We demonstrated that neglecting spatial dependencies in this type of studies can lead to several misinterpretations. We therefore advocate, that the design and enforcement of policy instruments—such as REDD+—should start from common international entry points that ensure for coherent agricultural and demographic policies. In order to achieve a long-term impact on the ground, these policies need to have enough flexibility to be modified and adapted to specific national, regional or local conditions.

Overheating risk assessment of different dwellings during the hottest season of a warm tropical climate

Cities with hot tropical climate suffer generally from warm conditions during all year long, which could result on buildings ‘overheating’ or high energy consumption by cooling. This paper is the first of its kind in Central America, region that lacks studies regarding thermal performance of buildings. This study develops an overheating risk assessment to twelve dwellings of Tegucigalpa, Honduras, with a warm tropical climate, based on 41-day field study measurements of indoor air temperatures during its hottest season of the year. The aim of the study was to find if overheating risk differed depending on the building typology, single-family (SD) or apartment-type (AT), and based on the latter, to what extent roof exposure to solar gains and material properties, such as u-values and thermal mass, are parameters that influence the risk of overheating. The adopted methodology followed CIBSE TM52 Overheating Risk Methodology, and EN15251 and ASHRAE 55 adaptive thermal comfort approaches. Overheating risk was found to vary depending on the residential building typology. Dwellings with high roof exposure and high u-values in roof were found to be ‘overheating’ more. Following CIBSE TM52 methodology, some AT and SD dwellings experienced hours of exceedance above 3% of occupied hours, reaching up to 12.5% (61 h) and 20.3% (133 h) of occupied hours, respectively. Passive strategies such as improving roof properties (e.g. low u-values), shading and night ventilation may be necessary to reduce the risk of overheating in Tegucigalpa and similar tropical contexts where air conditioning is less affordable.