Microclimatic Variables Research Articles

Environmental effects of a management method used after fire on development of temperate Scots pine ecosystem: a 15-year study from Poland

Due to the ongoing climate changes, temperate forests are increasingly exposed to fires. However, until now the functioning of post-fire temperate forest ecosystems with regard to used forest management method has been weakly recognized. Here, we examined three variants of forest restoration after fire (two variants of natural regeneration with no soil preparation—NR, and artificial restoration by planting following soil preparation—AR) regarding their environmental consequences in development of post-fire Scots pine (Pinus sylvestris) ecosystem. The study was conducted using a 15-year timespan in a long-term research site located in the Cierpiszewo area (N Poland) being one of the biggest post-fire grounds in European temperate forests in last decades. We focused on soil and microclimatic variables as well as on growth dynamics of post-fire pines generation. We found that the restoration rates of soil organic matter, carbon and most studied nutritional elements stocks were higher in NR plots than in AR. This could be primarily linked to the higher (p < 0.05) density of pines in naturally regenerated plots, and the subsequent faster organic horizon reconstruction after fire. The difference in tree density also involved regular differences in air and soil temperature among plots: consistently higher in AR than in both NR plots. In turn, lower water uptake by trees in AR implied that soil moisture was constantly the highest in this plot. Our study delivers strong arguments to pay more attention to restore post-fire forest areas with the use of natural regeneration with no soil preparation.

Applied nucleation under high biodiversity silvopastoral system as an adaptive strategy against microclimate extremes in pasture areas.

This study aimed to assess the influence of the high biodiversity silvopastoral system (SPSnu) on the microclimate, pasture production, and pasture chemical composition. Microclimate variables and pasture production and chemical composition were measured in pared paddocks under SPSnu and treeless pasture (TLP) in a commercial farm during four seasons in Southern Brazil. SPSnu measurements were subdivided into two areas: around the nuclei (AN) and area inter-nuclei (IN). In the TLP paddocks, we plotted fictitious nuclei with the same areas and distributions of SPSnu, however without trees. For the microclimate measurements, these areas were noted when shaded or unshaded by the nuclei trees. In each season, the microclimate variables air temperature (AT, °C), relative humidity (RH, %), illuminance (Ilu, lux), wind speed (WS, m/s), and soil surface temperature (SST, °C) were measured. In addition, botanical composition (%), pasture production (kg/DM/ ha), and pasture chemical composition were evaluated. The SPSnu provided the lowest values of microclimate variables in all seasons (p < 0.05), except for the relative humidity. Winter had the highest thermal amplitude in the systems. The highest difference between SPSnu and TLP for AT (4.3°C) and SST (5.2°C) was measured during the hot seasons (spring and summer). In contrast, during cold seasons (autumn and winter) it observed highest thermal amplitude between SPSnu and TLP. Overall, the highest annual pasture production was observed in the SPSnu (p < 0.05). During the summer, the SPSnu areas showed the highest values of crude protein and dry matter (p < 0.05). During the winter, the TLP showed the lowest values (p < 0.05) of pasture production and dry matter. It was observed that SPSnu improved the microclimate at the pasture level, influencing pasture production and pasture chemical composition. The enhanced microclimate can partially mitigate some of the effects of climate change on pastoral agroecosystems, creating conditions for ecological rehabilitation of ecosystem processes and services. These conditions could be amplified to a biome level through a payment for ecosystem services program.

Effect of urban microclimates on dynamic thermal characteristics of a vehicle cabin

The external climate consistently maintains thermal transfer with the vehicle cabin. The complexity and variability of the urban microclimate cause dynamic changes in the thermal characteristics of the cabin. Combining the differences in spatial structure and environmental characteristics of urban roads, this study proposed a cabin thermal management method based on matching cooling schemes for different urban microclimates in road space, aiming to achieve thermal comfort and low energy consumption. Environmental load spectrum tests were conducted in three types of urban road spaces during the summer in southern China, including open roads, boulevards, and underground parking lots. The primary environmental loads experienced by the vehicle in service are solar radiation, high temperature, and high humidity. However, these loads vary significantly due to factors such as cloud cover, building and tree shading, and tree transpiration. Combined with the cabin thermal model, the study analyzed the effect of environmental differences in road scenes on the dynamic thermal characteristics of the vehicle cabin, and explored the variability of passengers’ cooling requirements. The results indicated that the HVAC air supply temperatures of 10.5°C, 15.8°C and 20.5°C should be respectively adopted on the open road, boulevard and in the underground parking lot.

Analysis of a City's Heat Island Effect on the Micro-Climate Parameters within Cities

The Urban Heat Island (UHI) is a micro-climatic phenomenon that influences the urban areas by elevating its temperature. UHI not only causes the thermal discomfort but also exert serious health issues along with aggravation of urban microclimate. Although a lot of research has been done on this phenomenon but UHI effect on micro scale is still less explored. This paper attempts to make a contribution in UHI studies of micro-climate. It consists of examination of UHI impact on microclimate of Aligarh city areas using mobile traverse method. This study determined the presence and extent of UHI’s microclimate variation within urban communities of different environmental layout and functional uses. The UHI effect started to appear from early afternoon and continue to rise with maximum UHI intensity recorded at early night. The highest recorded UHI intensity was 3.1 °C (at 21:00 hrs.), and the lowest was 0.6 °C (at 09:00 hrs.). A comparison of two districts of the same city located at a distance of 3 km and differing in population density, the number of buildings and landscaping showed that in the L1 area with more dense population and low landscaping, the temperature was consistently higher during the daily period; also in the L1 region had less humidity, which, combined with the already high temperature, makes it difficult to breathe and control the microclimate. These findings can be used for consideration for the future sustainable development of the affected area in regard of thermal comfort, environmental health and urban planning.

How Can a Changing Climate Influence the Productivity of Traditional Olive Orchards? Regression Analysis Applied to a Local Case Study in Portugal

Nowadays, the climate is undoubtedly one of the main threats to the sustainability of olive orchards, especially in the case of rainfed traditional production systems. Local warming, droughts, and extreme weather events are some of the climatological factors responsible for environmental thresholds in relation to crops being exceeded. The main objective of this study was to investigate the influence of microclimatic variability on the productivity of traditional olive orchards in a municipality located in northeastern Portugal. For this purpose, official data on climate, expressed through agro-bioclimatic indicators, and olive productivity for a 21-year historical period (2000–2020) were used to evaluate potential correlations. In addition, a comprehensive regression analysis involving the dataset and the following modeling scenarios was carried out to develop regression models and assess the resulting predictions: (a) Random Forest (RF) with selected features; (b) Ordinary Least-Squares (OLS) with selected features; (c) OLS with correlation features; and (d) OLS with all features. For the a and b scenarios, features were selected applying the Recursive Feature Elimination with Cross-Validation (RFECV) technique. The best statistical performance was achieved considering nonlinearity among variables (a scenario, R2 = 0.95); however, it was not possible to derive any model given the underlying methodology to this scenario. In linear regression applications, the best fit between model predictions and the real olive productivity was obtained when all the analyzed agro-bioclimatic indicators were included in the regression (d scenario, R2 = 0.85). When selecting only the most relevant indicators using RFECV and correlation techniques, moderate correlations for the b and c regression scenarios were obtained (R2 of 0.54 and 0.49, respectively). Based on the research findings, especially the regression models, their adaptability to other olive territories with similar agronomic and environmental characteristics is suggested for crop management and regulatory purposes.

Higher temperature variability in deforested mountain regions impacts the competitive advantage of nocturnal species.

Deforestation is a major contributor to biodiversity loss, yet the impact of forest loss on daily microclimate variability and its implications for species with different daily activity patterns remain poorly understood. Using a recently developed microclimate model, we investigated the effects of deforestation on the daily temperature range (DTR) in low-elevation tropical regions and high-elevation temperate regions. Our results show that deforestation substantially increases DTR in these areas, suggesting a potential impact on species interactions. To test this hypothesis, we studied the competitive interactions between nocturnal burying beetles and all-day-active blowfly maggots in forested and deforested habitats in Taiwan. We show that deforestation leads to increased DTR at higher elevations, which enhances the competitiveness of blowfly maggots during the day and leads to a higher failure rate of carcass burial by the beetles at night. Thus, deforestation-induced temperature variability not only modulates exploitative competition between species with different daily activity patterns, but also likely exacerbates the negative impacts of climate change on nocturnal organisms. In order to limit potential adverse effects on species interactions and their ecological functions, our study highlights the need to protect forests, especially in areas where deforestation can greatly alter temperature variability.

Drivers of Forested Riparian Microclimate on the Olympic Peninsula of Washington State

Riparian zones have unique microclimates that support distinct assemblages of aquatic and terrestrial species, which in recent decades have resulted in a regulatory emphasis on riparian protections. However, an understanding of the drivers of riparian microclimate is still lacking. This study examined drivers of variability in summer air temperature and vapor pressure deficit in the riparian zones of 10 drainage basins (31 to 789 ha) on the western Olympic Peninsula, Washington. Model selection analysis was used to explore hypotheses about the influences of 3 types of drivers on microclimate: regional climate gradients, proximity to stream, and solar radiation. Proximity to stream had the strongest influence on microclimate; the air became warmer and drier with increasing distance from the stream and with increasing steepness of the stream valley slope. Basins at lower elevations (range = 28 to 362 m) had cooler, more humid microclimates, a pattern attributed to marine influence. Variation in microclimate was also associated with variation in solar exposure, modeled as a function of topography. Testing of canopy closure influence on microclimate was hindered by uniformly high canopy closure across the study area (87 to 98%) as a result of unmanaged, primarily second-growth stream buffers. Each of the microclimate drivers identified in this study was a function of topography, across a range of scales. By understanding these relationships between topographic variation and riparian microclimate, managers and researchers will be able to more accurately and efficiently delineate the extent of riparian microclimate influence.

Termitarium morphological and microclimatic variations in an agricultural landscape

Termitarium morphological and microclimatic variations in an agricultural landscape

Long‐term capture data uncover shifts in the daily activity patterns of Amazonian birds

Although the duration of biological rhythms varies from milliseconds to decades, daily cycles are especially widespread for individual organisms. These circadian rhythms are synchronized by light–dark cycles, which govern predictable changes in other microclimate variables. Despite the fixed, regular nature of these abiotic cycles at low latitudes, little is known about how different animals structure activity along these gradients. We used 25 years of capture–recapture data and ~ 25 000 unique captures to characterize ‘activity' (time of capture) for 65 species of Amazonian birds in the lowest forest stratum (0–2.5 m). To quantify vertical niche breadths, we also measured foraging heights for these same species in the field. Activity peaked within the first two hours after sunrise for most species (71%), while others peaked 1–3 h later (29%). This difference was associated with an apparent preference for specific vertical strata, as terrestrial and near‐ground birds peaked ~ 1 h after sunrise, while birds from higher strata delayed their first bouts of activity in the lower understory (by an average of 40–100 min). Peak capture times also correlated with long‐term abundance trends, as only species with the earliest capture times showed strong declines, suggesting that associations with mid‐ or late morning microclimates may contribute to resiliency in birds typical of higher strata. Because arboreal species largely avoid the lower understory in the early morning, when terrestrial birds are active, we infer that they are poorly adapted to low light environments. However, with their broad vertical niches and reliance on brighter microhabitats, we suggest that an arboreal lifestyle diminishes specialization and may increase the capacity to cope with a wider range of daily microclimate conditions. We predict that subtle, but important, shifts in daily activity patterns would materialize if other biodiversity‐monitoring programs could analyze similar temporal datasets.

Strong amplification of mid-infrared radiation absorption in nanotube-confined water

Energy absorption on a nanometer scale is vital for biochemical and climate systems. This paper reports that a two times amplification in absorption efficiency of mid-infrared (MIR) radiations can be achieved by water molecules confined in carbon nanotubes with a small radius compared to the bulk water absorption. This absorption enhancement is closely associated with the configurational change of water molecules into a unidirectional alignment under the nanotube confinement, which greatly augments the transition probability concerning the MIR absorption. In addition, the effect of confinement due to a (6,6) carbon nanotube is found to be very robust, equivalent to that of a 5 V/nm static electric field. These findings can be used to design energy-efficient nanodevices to modulate the microclimate variables by converting the redundant ambient MIR irradiation into the prompt heat conduction and are instructive for understanding the specific functioning of relevant biological channels.

Heat ameliorative measures in Murrah buffalo (Bubalus bubalis) heifers during summer: effect on microclimate, thermal comfort, and behavior.

Water buffalo (Bubalus bubalis) is the mainstay of milk production in Asian countries including India. However, the hot climate of the country remains the biggest bottleneck to exploit the potential of this species. Therefore, a study was conducted to assess the effect of heat ameliorative measures on microclimate, thermal comfort, and behavior of Murrah buffalo heifers during summer. Buffalo heifers (n = 24) between the age of 15 and 20months with a mean body weight of 363.75 ± 11.27kg were randomly grouped into four treatments based on their age and body weight. The heifers kept in the shed without any cooling served as CON (control), while the animals of group CJ were tied with a cooling jacket. The buffalo heifers of the CJF group were subjected to the cooling jacket with forced air ventilation, whereas the intermittent (10min at 2-h intervals) sprinkling followed by forced air ventilation was practiced in group SF between 900 and 1800h throughout the experiment. The microclimatic variables were low in the sheds of groups CJ, CJF, and SF than the CON. The physiological responses such as rectal temperature, skin temperature, respiration rate, and pulse rate were reduced in groups CJ, CJF, and SF than the CON at 1400h. The serum cortisol was less in the CJF and SF than those of CON group. The animals of the CJ, CJF, and SF groups spent more time for feeding and rumination with less frequent longer bouts. The extended periods of lying followed by shorter standing and idling were observed in groups CJ, CJF, and SF when compared with the CON. It may be therefore concluded that cooling jacket and intermittent sprinkling in combination with forced air ventilation might be helpful in improving the micro-environment, thermal comfort, and behavior of buffalo heifers particularly under tropical climates during summer.

A guide and tools for selecting and accessing microclimate data for mechanistic niche modeling

AbstractMost ecological analyses and forecasts use weather station data or coarse interpolated, gridded air temperature data. Yet, these products often poorly capture the microclimates experienced by organisms that respond to fine‐scale spatial and temporal environmental variation near the surface. Sources of historic and projected future data with finer spatial and temporal resolution are proliferating. We qualitatively and quantitatively review and evaluate the available data on three core issues central to microclimate modeling: the quality of the input environmental data, the ability of algorithms to capture microclimatic processes given environmental forcing data, and how best to access microclimatic data. We show how differences between observed environmental conditions and those estimated using environmental forcing data, microclimate algorithms, and precomputed microclimate datasets can be substantial depending on the variable, location, and season. The choice of environmental dataset to parameterize biophysical models has ramifications for biological estimates, such as the duration of potential activity and incidence of thermal stress. New data sources offering high temporal and spatial resolution correspond well to observational data and have the potential to revolutionize understanding of the ecological implications of microclimate variability. We provide resources to help users select and access appropriate environmental data for biological applications, including users' guides and interactive visualization, to better infer how organisms experience climate variability and change.

Microclimate and its influencing factors in residential public spaces during heat waves: An empirical study in Hong Kong

Creating thermally comfortable living environment under the new normal of heat waves requires pertinent knowledge as references. In subtropical residential areas, various types of public spaces exist, whose microclimate differences during heat waves, as well as their relationship with surrounding building and greenery characteristics, have not been systematically investigated. We therefore evaluated microclimate performances in three typical types of residential public spaces, i.e., open squares, vegetated spaces, and semi-outdoor spaces, and their relationship with surrounding built environment during summertime heat waves. Field measurement of microclimate parameters was conducted in two selected public housing estates in Hong Kong, followed by calculation of thermal comfort indices. Their relationship with building and greenery factors was analyzed. Results show inconsistent patterns in different microclimate variables among three types of spaces across different times of the day, while thermal comfort conditions in the three types of spaces are significantly different. In vegetated spaces and open squares, three-dimensional factors play dominant roles in determining microclimate and thermal comfort condition, with sky view factor (SVF) contributing the most. We detected key SVF threshold for effective thermal comfort enhancement around 0.4, based on which we discussed building and greenery optimization in similar urban context from a point-based SVF perspective and its potential application in practice. In semi-outdoor spaces, two-dimensional land-cover composition contributes greater than three-dimensional factors. This study provides empirical evidence on thermal performance of residential public spaces, which can assist practitioners in achieving adaptation to heat waves in high-density urban contexts in subtropical regions.

Effects of mesoclimate and microclimate variations mediated by high altitude and row orientation on sucrose metabolism and anthocyanin synthesis in grape berries

Climate change and extreme weather pose significant challenges to the traditional viticulture regions. Emerging high-altitude grape-producing regions with diverse orientations have shown great potential in coping with this challenge. Stable, high-quality wine grape production may be achieved by synchronizing the meso- and microclimate. To clarify the role of high altitude and row orientation in meso- and microclimate and the response of berries to it, we evaluated seven years (2012–2018) of climate data, two years of basic grape (Cabernet Sauvignon, Vitis vinifera L.) quality, and one-year microclimate from veraison to harvest. By comparing two locations (Sidon 2 047 m, Sinon 2 208 m) in Yunnan Province, China, we found that the average temperature has been stable at approximately 15 °C for seven years, with no extreme weather or, noticeable global warming. The light intensity (LI) in the north-south (NS) was more balanced than the east-west (EW) direction, and the east-west to the south (EW-S) canopy side was almost higher than the other sides. High LI was associated with high photosynthetically active radiation (PAR), ultraviolet (UV), and infrared (IR) light and vice versa. The north-south to the east (NS-E) and east-west to the north (EW-N) sides were characterized by lower LI and higher UV and IR light, and higher total anthocyanin content. Most anthocyanin synthesis-related genes, for example, VvF3′H and VvF3′5′H, were highly expressed in NS-E from veraison to maturity. Perhaps UV and IR light induced their expression. This study provides new insights on the role of differently orientated rows in controlling grape quality due to varied light quality. The findings are globally significant, particularly in the context of climate change, and offer fresh insights into berry physiological responses and decision-making for the management of existing vineyards.

Tree Traits and Microclimatic Conditions Determine Cooling Benefits of Urban Trees

Trees play a key role in mitigating urban heat by cooling the local environment. This study evaluated the extent to which street trees can reduce sub-canopy air temperature relative to ambient conditions (ΔT), and how ΔT relates to tree traits and microclimatic variables. Air temperature under the canopies of 10 species was recorded within residential areas in Western Sydney, Australia, during summer 2019–2020. Tree and canopy traits, namely tree height, specific leaf area, leaf dry matter content, leaf area index, crown width and the Huber value (the ratio of sapwood area to leaf area) were then measured for all species. Species differed significantly in their ΔT values, with peak cooling (maximum ΔT −3.9 °C) observed between 9–10 am and sub-canopy warming (i.e., positive ΔT values) typically occurring during afternoon and overnight. Trees with high LAI and wider canopies were associated with the greatest daytime cooling benefits and lower levels of nighttime warming. ΔT was also negatively related to windspeed and vapor pressure deficit, and positively to solar irradiance. This study provides valuable information on how tree characteristics and microclimate influence potential cooling benefits that may aid planning decisions on the use of trees to mitigate heat in urban landscapes.

Microclimate analysis of high-density urban residential open enclosures: A case of Thane, India

Urban heat island produces a significant impact by modifying the microclimate in urban areas. To ensure good quality of life with a safe and healthy built environment, the floor space index (FSI) can be an effective tool. It helps to control the urban densities and shape the morphology of the built environment. Taking the case of typical residential development in a densely populated Indian city, an attempt has been made to explore the relationship between FSI and the microclimate of such open spaces that perform like an open enclosure (OE). Adopting the simulation pathway in ENVI-met, a mathematical relationship is established between an important tool used by urban planners and the variables of the microclimate in a typical urban enclosure. The observations indicate that FSI has a strong negative correlation with air temperature and mean radiant temperature. Evaluation of physiological equivalent temperature reveals a similar relationship with FSI, demonstrating a temporal transposition of the trend for a particular FSI range of 2.5-3.5 in the late evening and early morning hours due to high humidity levels and reduced wind speeds. The study will help the planners to prognosticate the microclimatic variables while working out the data-based, logical and well-evaluated future development control regulations.

Local variability of a taiga snow cover due to vegetation and microtopography

ABSTRACT The taiga snow cover accumulates in relatively stable and windless weather. This should produce a uniform snow cover with continuous, laterally homogeneous stratigraphy and snow properties when the snow is deposited on a level, smooth substrate. However, such substrates are rare, and local variations in vegetation and ground surface topography alter the structure of the snow cover and produce irregular snow layers. In this study, we investigated the effects of vegetation, microtopography, and microclimatic variability on the taiga snow near Fairbanks, Alaska. Through the winter of 2019–2020, in situ measurements were made at three locations with distinctly different local microtopographic features and radically different (but typical) vegetation. One site was an open grassy field, the second a mature spruce forest, and the third a birch forest located on thermokarst terrain with steep microrelief where ice wedges had degraded. Widely different canopy interception processes proved to have the strongest impact on the resulting snow cover heterogeneity by altering the initial deposition, with surface microtopography having the second strongest influence through postdepositional processes. In this article, we suggest a conceptual framework for understanding and modeling taiga snow variability in terms of the vegetation and microtopography that created it.

Estimating the potential drivers of dispersal outcomes for juvenile gopher frogs (Rana capito) using agent-based models

Among mobile terrestrial animals, movement among microsites can allow individuals to behaviorally moderate their body temperatures and rates of water loss, which can have important consequences for activity times, growth, fecundity, and survival. Ground-layer vegetation can change the availability and variability of microclimates; however, gaps in our understanding of how individuals interact with the microclimates created by vegetation limit our ability to inform management actions for wildlife. Amphibians can simultaneously balance operant body temperatures and water loss and the availability of heterogeneous microclimates should moderate how effectively they are able to do so. However, relatively few studies have attempted to mechanistically demonstrate how ground vegetation-driven effects on microclimatic variation may affect amphibian performance and survival. Agent-based modeling (ABM) can incorporate behavior and other mechanisms to understand how animals interact with their environments to result in larger scale patterns. They are effective for exploring alternative scenarios and representing the uncertainty in systems. Here, we use ABMs to integrate field and laboratory measurements of movement behavior, physiology, and plant effects on near-ground microclimate to explore how ground vegetation and the availability of terrestrial refugia may affect the survival and terrestrial distributions of juvenile gopher frogs (Rana capito) under two weather regimes. We also examine how assumptions regarding micro-scale movement (&amp;lt; 1 m2) affect the influence of ground vegetation on survival and settlement within refugia. While all variables affected settlement and survival, our models predict that inter-annual variation in weather and the density and spatial distribution of permanent refugia likely have the greatest influence on juvenile survival. The benefit of increased ground vegetation was dependent on the reasonable assumption that gopher frogs exhibit microclimate habitat selection throughout the day and night to limit water loss. Our models suggest that vegetation would be most beneficial to amphibians under warmer weather regimes provided there is sufficient rainfall.

Environmental heterogeneity increases the conservation value of small natural features in karst landscapes

Local biodiversity hotspots are often located within regions where extreme and variable environmental – e.g., climatic and soil – conditions occur. These areas are conservation priorities. Although environmental heterogeneity is recognised as an important determinant of biodiversity, studies focusing on the effects of multiple environmental heterogeneity components in the same ecosystem are scarce. Here we investigate how topography and related microclimatic variables and soil properties may influence the biodiversity and conservation value of karst landscapes. Karst landscapes of the world contain millions of dolines (i.e. bowl- or funnel-shaped depressions) that may function as ‘small natural features’ with a disproportionately large role in maintaining biodiversity relative to their size. We assessed the diversity of microclimates, soils and vegetation and their relationships in six microhabitats (south-facing slopes, east-facing slopes, west-facing slopes, north-facing slopes and bottoms of dolines, and the adjacent plateau) for nine large dolines in a grassland ecosystem. Although there were remarkable differences among the conservation value of these microhabitats (e.g., representation of different species groups, presence of ‘climate relicts’), each microhabitat had an important role in maintaining species that are rare or absent in other microhabitats in the landscape. We found that the studied dolines exhibited highly variable environmental conditions and promoted a high diversity of vegetation types with unique species composition, contributing to the topographic, climatic, soil, vegetation and land cover heterogeneity of karst landscapes. Therefore, our findings highlight that dolines may function as local biodiversity hotspots and have a crucial conservation importance. As dolines are widespread topographic features in many karst landscapes throughout the world, our results could be directly applied to other regions as well. An integrated approach is urgently needed to provide guidelines for landscape management, promoting the retention of the microhabitat diversity of small natural features for species vulnerable to climate change and/or various disturbances.

Heat stress increases risk taking in foraging shorebirds

Abstract Animals often face a trade‐off between food acquisition and predation/disturbance avoidance. Yet, the extent to which this trade‐off is affected by modulating factors such as thermal risk and foraging opportunities has been largely overlooked. Here, we examined the influence of temporal and environmental gradients on the flight initiation distance (FID, the distance at which animals flee from an approaching human‐simulated predator) and escape mode (flying/low risk versus running/low cost) in 16 species of shorebirds foraging on tidal flats of the Bijagós Archipelago, Guinea‐Bissau. We measured escape responses throughout the low tide period during wet and dry seasons and simultaneously recorded microclimate variables and occurrence of heat‐reduction behaviour (ptiloerection). Furthermore, we measured corticosterone metabolites (CORTm) from droppings in red knots Calidris canutus to assess whether ptiloerection is associated to a physiological stress response to hot conditions. Overall, birds tolerated a closer approach at higher environmental temperatures and when showing ptiloerection. They also had shorter FIDs during the dry season and towards the start/end of the low tide period. FIDs also increased with body mass and decreased in areas with more human presence. In red knots, individuals showing ptiloerection had higher levels of CORTm, demonstrating a link between physiological and behavioural stress coping responses to heat events. Our results suggest that heat‐stressed shorebirds take greater risks, supporting the idea of a thermoregulation–predation risk trade‐off. They also indicate that shorebirds adjust risk taking to tidal and seasonal cycles, generally reducing FIDs when the energetic costs of escape are expected to be large. Finally, they suggest that shorebirds habituate to non‐lethal human presence and respond to perceived predation risk in accordance with the predictions of optimal escape theory. These results are relevant to many animals that face a tight window for foraging activity while being exposed to predation/disturbance and heat during the day. We discuss management implications of our results in the context of global change. Read the free Plain Language Summary for this article on the Journal blog.