Logged Forests Research Articles

Short‐term impacts of selective logging on forest elephants

AbstractAlthough forest elephants (Loxodonta cyclotis) are known to use logged forests, the impact of selective logging on this critically endangered species has never been well established. Considering the potential of some logged areas to serve as other effective area‐based conservation measures, aligning with the Convention on Biological Diversity's 30/30 initiative, we aimed to assess the short‐term impacts of logging on three population parameters: the presence, abundance, and activity of forest elephants. Combining camera traps and dung surveys before and after logging operations, we assessed the response of forest elephants in a certified timber concession in Gabon. Encouragingly, we found no negative effects of logging on the three population parameters studied. There was no discernible change in the presence of elephants after logging, and their abundance actually increased (relative abundance index from 1.56 to 2.59; p‐value 0.0139) at one of the study sites. Activity patterns were also unaffected, showing sustained activity during daylight hours. We also identified the logging‐associated factors that have significantly influenced forest elephant's abundance. Notably, logging intensity, as measured by the average number of trees harvested per hectare, and road density were positively correlated with the number of forest elephant observations (logging intensity effect: 0.2992, p‐value 0.035; road density effect: 0.3628, p‐value 0.060). As global conservation goals evolve, this research provides important insights into the coexistence of well‐managed industrial activities and the conservation of endangered species, highlighting the need to include responsibly managed timber concessions in future conservation strategies. It also underscores the importance of wider adoption of sustainable practices such as low‐impact logging, promoted by certification schemes such as FSC or PEFC, to secure the future of central African forests and their unique wildlife.

Tropical forest clearance impacts biodiversity and function, whereas logging changes structure.

The impacts of degradation and deforestation on tropical forests are poorly understood, particularly at landscape scales. We present an extensive ecosystem analysis of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 82 variables categorized into four ecological levels spanning a broad suite of ecosystem properties: (i) structure and environment, (ii) species traits, (iii) biodiversity, and (iv) ecosystem functions. Responses were highly heterogeneous and often complex and nonlinear. Variables that were directly impacted by the physical process of timber extraction, such as soil structure, were sensitive to even moderate amounts of logging, whereas measures of biodiversity and ecosystem functioning were generally resilient to logging but more affected by conversion to oil palm plantation.

Stable nutrient utilization of trees promotes community biomass accumulation in Korean pine and broad-leaved mixed forests after logging.

The recovery of community productivity in disturbed temperate forests is affected by fluctuating nutrient environments. How plant growth achieves high biomass accumulation in a limited nutrient environment remains unclear but may be attributed to the flexibility of plant nutrient utilization. Nutrient homeostasis (H) reflects the ability of plant tissues to maintain a relatively constant N and P content under nutrient fluctuations and represents flexible or stable plant nutrient utilization. We aim to reveal the influence of plant nutrient utilization mechanisms on community biomass accumulation after logging. We chose 28 post-logged Korean pine and broad-leaved mixed forests after seven recovery periods (6, 14, 25, 36, 45, and 55 years after logging) with six low-intensity selective logged treatments and one unlogged treatment (100 years after logging). We then estimated the H value of leaf N (HN), leaf P (HP), and leaf N:P ratio (HN:P) and the biomass of 234 plant species with different functional groups, soil nutrient, and species diversity. The leaf HN of 13.19 and the leaf HP of 9.87 reached the maximum at 36 and 45 years after logging, respectively. The HN:P at the community level reached the maximum at 36 years after logging. The robust linear trend between nutrient H and biomass suggests the accumulation of biomass benefits from stable nutrient utilization after logging. Considering the soil nutrient and species diversity, nutrient H showed the major explanation of biomass accumulation in trees, herbs, and whole community. The stable N utilization of tree species accounts for the maximum independent contribution (25.05%) to the community biomass accumulation. Herb species with flexible P utilization had major contribution (37.97%) to herb biomass accumulation. Our study highlights the vital role of high HN in promoting community biomass accumulation in logged forest to assess forest sustainability.

The Impact of China’s Natural Forest Logging Ban on Chinese and International Timber Markets: A Counterfactual Analysis Based on Predicted Market Price

China’s implementation of the Comprehensive Commercial Logging Ban in All Natural Forests is deemed as disrupting the stability of both Chinese and international timber markets and has raised widespread concerns about deforestation leakage on a global scale. Clarifying the impact of the logging ban on the Chinese and international timber markets is essential for formulating effective policies and taking collaborative actions to improve the stability of both timber markets and promote the sustainable development of global forest resources. This study examines the causal effects of the logging ban on Chinese and international timber markets by conducting a counterfactual analysis of Chinese domestic and imported timber prices with the synthetic control method. Unlike most previous studies that revealed significant price increases in both markets as a result of the logging ban, our results show that there are no significant causal effects between the logging ban and the price changes in Chinese and international timber markets. As China made extensive efforts in plantation cultivation and harvesting and substantially improved its domestic timber supply capacity, the logging ban has only produced a limited impact on the Chinese domestic timber market and has not disrupted the international timber market through trade. Therefore, China’s logging ban policy has not protected its own forest resources at the expense of deforestation in other countries, and it has provided a practical reference for the formulation of forest protection policies and sustainable forest management.

Saproxylic beetle assemblages exhibit distinct seasonal patterns across different decay classes of dead wood in a mixed temperate forest

Abstract Saproxylic organisms play a pivotal role in the decomposition of woody materials, profoundly impacting nutrient cycling within forest ecosystems. With their rich biodiversity and diverse ecological functions, saproxylic species provide unique ecological services and interactions that are closely linked to specific dead wood types. Given the distinctive roles and diversity of saproxylic beetles, forest loss and management practices that reduce dead wood amount and quality pose a risk of greater biodiversity loss. This highlights the critical need for comprehensive research into saproxylic beetle diversity and community structures from various perspectives to support sustainable forest management strategies. We sampled 60 Quercus logs in a temperate mixed forest during both winter and summer, and reared saproxylic beetles using emergence traps. Consequently, we collected a total of 1793 saproxylic beetles from 27 families and 75 species across three decay classes. Season was a key environmental variable, clearly distinguishing saproxylic beetle assemblages between winter and summer. While decay class did not clearly differentiate the beetle assemblages in summer, it distinctly separated the assemblages in winter. Our findings indicate that saproxylic beetles are influenced by changing resource availability and microclimate, driven by environmental variables such as season. This variability reveals the overlooked biodiversity potential, emphasizing the need for continuous and comprehensive research to achieve conservation goals and improve understanding of saproxylic organisms.

Two remarkable liverworts from human-modified landscape in Eastern Amazonia: Cololejeunea minuscula Pócs and C. satioi sp. nov.

Two remarkable species of Cololejeunea were identified colonizing human-modified landscape in Eastern Amazonia. One is a new discovery for science, here described as Cololejeunea satioi sp. nov. (subg. Pedinolejeunea). It was found on leaves of understory treelets in selective logging forest featuring small to medium-sized clearings with an abundance of lianas, in comparison to natural forest. The other species, Cololejeunea minuscula Pócs (subg. Aphanolejeunea), is a new record for the Brazilian Amazon. It was collected in the same forest as C. satioi, in an agroforestry area characterized by a mix of regional fruit tree species and introduced hardwood species. A full description and illustration of the new species as well as comments on morphology, taxonomy and distribution of the two taxa are provided.

Long‐Term Impacts of Selective Logging in a Tropical Rainforest in the East Region of Cameroon

ABSTRACTAlthough selective logging has become the primary cause of degradation in many African countries, little is known about its long‐term effects. This study investigated the long‐term effects of selective logging on forest tree species diversity and dynamics in the East Region of Cameroon. Six permanent monitoring plots of 1 ha each in unlogged and logged forests were established in 2005 and a recensus in 2011. Each 1 ha plot was divided into 25, 20 × 20 m quadrats. Each 20 × 20 m quadrat was further divided into 16, 5 × 5 m subquadrats, where the diameter at breast height (DBH) of all trees ≥ 2 cm was measured. There was a decrease in plant species density and richness in all forest types. Sloetiopsis usambarensis was the most important species in the unlogged forests and forests logged 21 years ago. The most important family was Putrangivaceae, Euphorbiaceae and Violaceae in the unlogged forests and forests logged 11 and 21 years ago, respectively. The frequency distribution of stem size classes indicated a reversed J‐shape of tropical forests. The above ground biomass (AGB) recovered more than 50% in all forests, and the unlogged forest had the highest AGB (961.8 Mg/ha). Larger stems indicated a forest at a stage of recovery from disturbance. Silvicultural management should be considered.

A Bibliometric Review of the Impacts of Logging in Forests in Semi-Arid Zones

Forest massifs in semi-arid zones play an essential role in maintaining ecological balances and the livelihood of local communities. However, unsustainable logging in these regions can have devastating ecological, and socio-economic consequences. This bibliometric review aims to synthesize the available evidence regarding the impacts of logging in semi-arid ecosystem. Analysis of publication trends reveals a significant increase in research from 2008, reflecting a growing awareness of the issues related to sustainable forest management. The United States, Canada, Australia and China the most prominent countries in this field. The bibliometric analysis of the highlights major concerns related to climate change, clear-cutting, interactions with demographic dynamics and biogeochemical cycles. However, gaps remain, including a lack of data specific to semi-arid areas, limited understanding of the complex interactions between different dimensions of impacts, and insufficient integration of local perspectives and traditional knowledge. This review highlights the need to continue interdisciplinary and collaborative research efforts to ensure sustainable management of semi-arid forests in the face of current and future environmental challenges.

Fungal and beetle diversity in deciduous fine woody debris in spruce-dominated forests in relation to substrate quantity and quality

Deciduous fine woody debris (DFWD) is a common deadwood substrate type in boreal conifer-dominated forests, but it is usually present in low volumes, and its importance for deadwood dependent biodiversity is poorly understood. In this study, we investigated how DFWD-associated fungal and beetle diversity depends on local substrate availability and quality, and how species diversity differs between DFWD and coarse deciduous deadwood (birch logs) in boreal mixed spruce-dominated forests in southern Finland. We studied 25 forest plots (each 0.16 ha), measuring and sampling all pieces of DFWD with a diameter of 2–5 cm and minimum length of 50 cm. Wood-inhabiting fungi were surveyed from wood samples by DNA metabarcoding and saproxylic beetles were surveyed by bark sieving. Our results showed a clear positive relationship between DFWD abundance and the diversity of fungi and beetles. Tree species and decay class diversity were not important in explaining fungal and beetle diversity or community composition, possibly due to low degree of variation in DFWD quality among the study plots. DFWD hosted more diverse fungal assemblages than birch logs, including species of conservation concern, while no red-listed beetle species were observed on DFWD. Overall, species assemblages associated with fine and coarse deciduous deadwood were non-nested. Thus, DFWD represents a non-redundant complementary deadwood resource type alongside coarse deciduous deadwood in boreal forests.

Effects of Wildfire and Logging on Soil CO2 Efflux in Scots Pine Forests of Siberia

Wildfires and logging play an important role in regulating soil carbon fluxes in forest ecosystems. In Siberia, large areas are disturbed by fires and logging annually. Climate change and increasing anthropogenic pressure have resulted in the expansion of disturbed areas in recent decades. However, few studies have focused on the effects of these disturbances on soil CO2 efflux in the vast Siberian areas. The objective of our research was to evaluate differences in CO2 efflux from soils to the atmosphere between undisturbed sites and sites affected by wildfire and logging in Scots pine forests of southern Siberia. We examined 35 plots (undisturbed forest, burned forest, logged plots, and logged and burned plots) on six study sites in the Angara region and four sites in the Zabaikal region. Soil CO2 efflux was measured using an LI-800 infrared gas analyzer. We found that both fire and logging significantly reduced soil efflux in the first years after a disturbance due to a reduction in vegetation biomass and consumption of the forest floor. We found a substantially lower CO2 efflux in forests burned by high-severity fires (74% less compared to undisturbed forests) than in forests burned by moderate-severity (60% less) and low-severity (37% less) fires. Clearcut logging resulted in 6–60% lower soil CO2 efflux at most study sites, while multiple disturbances (logging and fire) had 48–94% lower efflux. The soil efflux rate increased exponentially with increasing soil temperature in undisturbed Scots pine forests (p < 0.001) and on logged plots (p < 0.03), while an inverse relationship to soil temperature was observed in burned forests (p < 0.03). We also found a positive relationship (R = 0.60–0.83, p < 0.001) between ground cover depth and soil CO2 efflux across all the plots studied. Our results demonstrate the importance of disturbance factors in the assessment of regional and global carbon fluxes. The drastic changes in CO2 flux rates following fire and logging should be incorporated into carbon balance models to improve their reliability in a changing environment.

Geochemical fingerprinting of Norway spruce from the Eastern Carpathians: Sr isotopic and multi-elemental signatures

Ensuring efficient wood traceability within procurement chains is essential for establishing sustainable forest management and minimizing environmental damage in countries that produce and export timber. While some progress has been made with key legislative reforms to tackle this issue, the effectiveness of law enforcement still relies on the availability of appropriate analytical tools to determine the provenance of wood. This study documents the Sr isotopic and multi-elemental signatures of Norway spruce trees in the Eastern Carpathians, Romania – an area known for intensive forest logging. The research focused on trees from Rodna, Rarău, and Călimani, analyzing tree rings from 1970 to 2020 to assess temporal variability and develop site-specific geochemical fingerprints. In conjunction with tree samples, corresponding soil, groundwater, and river samples were analyzed, providing a comprehensive view of the bioavailable 87Sr/86Sr ratios in these ecosystems. The study found a strong correlation between the Sr isotope ratios in the wood and those in corresponding water and soil samples, confirming that the wood accurately mirrors local geochemical signatures. The Sr isotope ratios were consistent across most of the cores from trees within the same site but varied among sites within the same region. Principal Component Analysis of the Sr isotopic and multi-elemental data highlighted closer clustering of samples from the Călimani area, though distinguishing the samples from the Rodna and Rarău regions proved more difficult due to overlapping data points. This study broadens our understanding of geochemical variability and its implications. The insights gained provide a valuable foundation for future research aimed at enhancing wood traceability methods.

Assessing the potential of species loss caused by deforestation in a mature subtropical broadleaf forest in central China

Deforestation is a major type of land use change to accommodate growing population, especially in developing countries. The risk of diversity loss due to habitat loss can be estimated using the species-area relationship based on abundance of each species. However, deforestation often occurs before there is any understanding of the impact of deforestation on tree diversity. Here, we assessed the potential effect of forest habitat destruction on the loss of species richness in a mature subtropical broadleaf forest in central China. We surveyed and constructed the species-area relationship for 54 400 m2 plots, and simulated habitat loss scenarios by randomly and aggregately sampling plots. Rank-abundance of the 21 tree species was best fitted by the Zipf-Mandelbrot model, and our sample size was sufficient by the criterion of Hill numbers at orders q = 0, 1, and 2. We found that the number of species lost due to habitat loss was well predicted by the random placement species loss-area loss curve, and was lower than that due to aggregated habitat destruction by less than one species. The probability of losing one species reached 40% when losing 16 plots by aggregated sampling, 10 plots fewer than that by random sampling. Moreover, the probability of losing two species was 10–22 % higher by aggregately sampling than that by randomly sampling when losing 17 – 34 plots (0.68 – 1.36 ha). Considering that aggregated deforestation is common in reality, the results imply that the number of tree species lost due to deforestation could be higher than the theoretical estimation. Our study suggests the importance of assessing the impact of deforestation on tree diversity before selective logging in subtropical forests.

Tree mortality by ecological groups in the amazon region: Influence of forest structure, soil characteristics, and extreme climatic events after logging

Mortality of remaining trees tends to increase after logging, and adapting forest management to climate change is another significant challenge to ensure the sustainability of forests, timber production, and provision of ecosystem services. This study investigated mortality in remaining trees (DBH ≥ 20 cm) in different ecological groups (pioneer, light-demanding, and shade-tolerant) during different phases of forest monitoring (initial, intermediate, and final), as well as their relationship with structural, climatic, and environmental characteristics. The research was conducted in five managed areas in the Brazilian Amazon (Jari, Km114, Km67, Peteco, and Moju) with continuous monitoring over six to 33 years. We analyzed a total of 212 permanent plots containing 62 pioneer species, 250 light-demanding species, and 304 shade-tolerant species. The mortality rate for the three monitoring phases in logged forests was 1.27 %, 1.49 %, and 0.75 % year−1, respectively, while the rate in unlogged forests was 1.04 %, 1.33 %, and 0.50 % year−1. In post-logging forests, mortality was high for pioneer and light-demanding species, especially in the initial phase. For shade-tolerant species, mortality rate was influenced by soil silt and sand content, presence of phosphorus, and total carbon content. In unlogged forests, forest structure variables such as average height and total basal area, soil characteristics like phosphorus content, and climate factors such as intensity of dry months were most important for pioneer and light-demanding species. In the intermediate and final monitoring phases in logged forests, tree mortality was related to soil characteristics like sand and clay content, total carbon, and cation exchange capacity. Extreme climatic events such as severe drought, El Niño, and extreme temperatures also influenced tree mortality, along with time elapsed after logging. These findings highlight the complex interaction between soil characteristics, climate, and forest structure and tree mortality and ecology. These correlations are crucial to understand mortality processes in logged and unlogged forests, underscoring the importance of these factors for managing and conserving these ecosystems in the face of extreme climatic events and forest management practices.

The impact of war on forest logging: Changes in logging practices in Syrian rural communities

Syria has been struggling with a prolonged and brutal war for over a decade, leaving much of the country in devastation and its forests severely degraded. While many studies have identified logging for firewood as a significant driver of deforestation during the war, there is a notable absence of research specifically addressing logging behavior within the context of war. This research seeks to address this gap by examining the changes in logging behavior among local communities, the effects of violence and socioeconomic variables on wood harvesting, the contribution of wood income to people's survival during the war. To do that, we conducted survey questionnaires in two coastal villages in Syria—Blouta and Nehel al Annaze—which experienced high and low levels of violence, respectively. Our findings reveal that logging activities increased once the war began, with more people involved in forest harvesting and average days spent logging per week significantly increasing from 1.5 to 4. Additionally, the war appeared to reduce the gender disparity in logging activities: before the conflict, women engaged in logging significantly more frequently than men, but this difference became insignificant during the war. The level of violence alone did not significantly affect the amount of wood logged per month. Furthermore, income generated from wood harvesting played a substantial role in bridging the gap between the monthly income needed to cover their basic necessities and the actual income of families in both villages by 46.94 % and 84.83 % of the gap in Nehel al Annaze and Blouta, respectively. These results highlight the crucial role of forest resources in supporting rural livelihoods during times of war. Post-war effective forest management will be vital to ensure the sustainable use and recovery of forest resources, supporting both ecological restoration and economic stability for the rural communities.

Relationship between changes in ground surface elevation and surface soil movement in areas around horizontal step works made from thin logs in a Japanese cypress forest

Relationship between changes in ground surface elevation and surface soil movement in areas around horizontal step works made from thin logs in a Japanese cypress forest

Law Enforcement Against Illegal Logging in The Jurisdiction of the Tejakula Buleleng Police Sector

The practice of illegal logging is generally carried out by individuals who have official permission from the government to carry out forest logging, such as holders of Forest Ruler Rights (HPH) concession permits, however, if it is further detailed, the perpetrators of illegal logging are organized groups. Law enforcement in overcoming the crime of illegal logging Tejakula Sector Police use 2 (two) means, namely: Penal efforts that focus more on the repressive nature, namely actions taken after the crime occurs with law enforcement and imposition of penalties for crimes that have been committed, and non-penal efforts, a countermeasure that focuses more on the preventive nature, namely actions in the form of prevention before the crime occurs. To solve the problems in this study, the research method is the type of normative legal research supported by conducting field observations with the interview process with the Tejakula Buleleng Sector Police Investigator. So the expected results in this study, the most substantial is the difference in interpretation in terms of administrative sanctions there is a blurring of legal norms in Article 18 paragraph (1) of Law Number 18 of 2013 concerning the prevention and eradication of forest destruction, because in its application or implementation sometimes there is overlap between the meaning of the sentence of the implementation of government coercion sanctions with administrative sanctions of forced money

Development of Long-Range, Low-Powered and Smart IoT Device for Detecting Illegal Logging in Forests

Development of Long-Range, Low-Powered and Smart IoT Device for Detecting Illegal Logging in Forests

Soil wetting triggered by selective logging in Bornean lowland tropical rainforests

Aboveground biomass removal and canopy opening by selective logging modifies soil moisture in the main root zone, impacting soil aeration and various biogeochemical processes in tropical production forests. This study investigated the relationship between canopy damage and topsoil (10 cm) moisture in two logged forests in Malaysian Borneo, while simultaneously controlling for logging intensity, time elapsed since historical logging, and spatial autocorrelation. Volumetric soil water content (VSWC), canopy height model (CHM), leaf area index (LAI), and historical logging data were collected from 84 transects placed subjectively in 15 sites exhibiting varying canopies. We generated an index (PC1) quantifying the magnitude of canopy structural degradation from canopy structure metrics (CSM) combining CHM and LAI data within a 20-meter buffer for each transect. PC1 was analyzed for its impact on VSWC across logging periods, and contrasted with topography. Spatial autocorrelation of VSWC was examined regarding to canopy conditions. VSWC was significantly higher in all logged forests (over 0.4 m3 m−3) comparing to non-disturbed forests (0.27 m3 m−3). The immediate wetting could be a result of extracting mature individuals of late-successional species holding large biomass, while the persistent wet condition may be due to retarded canopy and biomass recovery. In the study area, canopy structure was a stronger predictor of soil moisture than topography. The high soil moisture underneath the most degraded canopies presented the largest spatial extent of autocorrelation. This study revealed soil wetting after selective logging in humid tropical forests, driven by reduced transpiration from biomass loss rather than increased evaporative demand resulting from canopy opening. The elevation in soil moisture could have disrupted biogeochemical processes in the below-ground system, which in turn impede forest succession and put stress on the overall vulnerability of disturbed tropical rainforests.

Structure of Ground Vegetation and Natural Regeneration of Tree Species in 12- to 15-Year-Old Bilberry Pine Forest-Clear-cut Complex of Middle Taiga Subzone.

Logging in mature stands where part of the forest is harvested in one or several cuts and part is retained (clearcutting and alternate strip cutting) results in the formation of an ecotone complex (EC), which includes a forest (F) zone, a forest edge (FE) as a transition from the forest to the clear-cut under the canopy, a clear-cut edge (CE) as a transition from the forest to the clear-cut outside of the canopy, and the clear-cut proper (C). The composition and structure of ground vegetation and natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., and Juniperus communis L.) were studied in a bilberry pine forest-clear-cut ecotone complex 12-15 years after stand removal. Specific structural features of ground vegetation and undergrowth (including tree regeneration) were observed in each of the four zones of the ecotone complex formed after logging of the mature forest. Atypical forest habitat (zone F) showed a minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and the highest abundance of the lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L. with a maximum height and a maximum yield of bilberry plants. The amount of tree regeneration in the FE zone was much the same as in the F zone. The projective cover, maximum shoot height, and yield of bilberry and the maximum shoot height of lingonberry in the FE zone were significantly lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut proper (C) strikingly differed from the forest (F and FE) zones of the ecotone complex by a greater number of deciduous and pine regeneration and a low abundance of dwarf shrubs. The clear-cut proper (C) differed from the CE zone by a higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.

Tropical beetles more sensitive to impacts are less likely to be known to science

Insects are posited to be declining globally. This is particularly pertinent in tropical forests, which exhibit both the highest levels of biodiversity and the highest rates of biodiversity loss. However, for the hyper-diverse tropical insects there are scant data available to evidence declines. Understanding tropical insect diversity and its response to environmental change has therefore become a challenge, but it is estimated that 80% of tropical insect species remain undescribed1. Insect biodiversity predictions are based mostly on well-studied taxa and extrapolated to other groups, but no one knows whether resilience to environmental change varies between undescribed and described species. Here, we collected staphylinid beetles from unlogged and logged tropical forests in Borneo and investigated their responses to environmental change. Out of 252 morphospecies collected, 76% were undescribed. Undescribed species showed higher community turnover, reduced abundance and decreased probability of occurrence in logged forests. Thus the unknown components of tropical insect biodiversity are likely more impacted by human-induced environmental change. If these patterns are widespread, how accurate will assessments of insect declines in the tropics be?