Forest Decline Research Articles

Last-Century Forest Dynamics in a Highland Pyrenean National Park and Implications for Conservation.

Ecological records from before and after the creation of natural parks are valuable for informing conservation and management but are often unavailable. High-resolution paleoecological studies may bridge the gap and provide the required information. This paper presents a 20th-century subdecadal reconstruction of vegetation and landscape dynamics in a national park of the Pyrenean highlands. The park lands had traditionally been used for cultivation, extensive grazing, forest exploitation, and hydroelectricity generation following the damming of numerous glacial lakes. A significant finding is that forests have dominated the landscape, with negligible changes in composition, and only experienced fluctuations in forest cover, influenced by both climatic and anthropogenic factors. The creation of the park (1955) and the initial restrictions on forest exploitation did not significantly affect vegetation cover or composition. Major forest expansion did not occur until several decades later, 1980, when the park was enlarged and forest exploitation was further restricted. This expansion peaked in the 1990s, coinciding with a warming trend and a decrease in fire incidence, before declining due to warmer and drier climates. This decline was coeval with the ongoing global forest dieback and may be exacerbated by the predicted global warming in this century, which could also increase fire incidence due to dead-wood accumulation. Currently, the main threats are global warming/drying, fire, and tourism intensification. Similar high-resolution paleoecological records in protected areas are globally scarce and would be capable in providing the long-term ecological scope required to properly understand forest dynamics and optimize conservation measures.

Emergency policies are not enough to resolve Amazonia’s fire crises

The fire crises in the Amazon continues to increase the risk of large-scale forest dieback, threatening regional biodiversity and global climate. This issue gained international attention in 2019 when fires in the Brazilian Amazon led to a fire ban imposition. Despite the uncertainty of its impact, the fire ban was reenacted in subsequent years. Here we assess the effectiveness of each fire ban by comparing observed fire counts with climate-driven predictions of fire for 2019–2021. While the 2019 ban likely reduced the number of fires to expected levels, it was largely ineffective in the years that followed. Four years later in 2023 under a different political dynamic, the Brazilian Amazon faced another fire crisis. Resolving this recurrent issue requires interventions that target the underlying causes of fire and extend beyond emergency measures, including long-term strategies focused on landscape management, public awareness and education, and engagement with local communities and stakeholders.

Drought- and heat-induced mortality of conifer trees is explained by leaf and growth legacies.

An increased frequency and severity of droughts and heat waves have resulted in increased tree mortality and forest dieback across the world, but underlying mechanisms are poorly understood. We used a common garden experiment with 20 conifer tree species to quantify mortality after three consecutive hot, dry summers and tested whether mortality could be explained by putative underlying mechanisms, such as stem hydraulics and legacies affected by leaf life span and stem growth responses to previous droughts. Mortality varied from 0 to 79% across species and was not affected by hydraulic traits. Mortality increased with species' leaf life span probably because leaf damage caused crown dieback and contributed to carbon depletion and bark beetle damage. Mortality also increased with lower growth resilience, which may exacerbate the contribution of carbon depletion and bark beetle sensitivity to tree mortality. Our study highlights how ecological legacies at different time scales can explain tree mortality in response to hot, dry periods and climate change.

Towards sustainable mangrove-shrimp aquaculture through capacity building and partnership in the Mekong River Delta

Vietnam, the world’s third-largest shrimp producer, witnessed a surge in shrimp farming when rice fields were converted into ponds, aiming to alleviate poverty in the Mekong River Delta (MRD). However, this growth significantly contributed to the decline of mangrove forests, as indicated by empirical and geospatial data. Local authorities have encouraged the application of “International Principles” to promote sustainable mangrove-shrimp aquaculture in MRD provinces. Tra Vinh, a province with a high rate of mangrove-shrimp farming, faces challenges in applying international standards, particularly for small-scale farmers. Understanding the circumstances in Tra Vinh is crucial not only for local farmers but also for stakeholders in the region. An in-depth review, local needs assessment, and a capacity-building program centred on the Asian Seafood Improvement Collaborative (ASIC) standards were conducted in Tra Vinh. The findings suggest that adhering to ecological/organic shrimp farming based on international standards is the right direction for local shrimp farmers. However, increased awareness alone does not guarantee a shift from traditional to internationally certified sustainable shrimp farming. The study highlights the role of private-private partnerships (PPPs) in facilitating the transition to sustainable mangrove-shrimp farming, emphasising that sustainable practices in the MRD are essential for household income, mangrove forest protection, environmental conservation, and climate resilience.

Combined 2D- and 3D ERT monitoring as a geophysical tool for investigating spatial and temporal soil moisture fluctuations in a pine-beech forest

As climate change continues, forests are increasingly suffering from drought stress, which is leading to widespread forest dieback, but also to increased mortality of individual trees. In this regard, the impact of small-scale differences in water availability on individual trees has not yet been sufficiently studied to determine possible responses of different tree species to future droughts. Since conventional soil moisture monitoring and sampling methods only consider single points or small volumes, Electrical Resistivity Tomography (ERT) is becoming increasingly important to cover a larger survey area and to detect small-scale heterogeneities with regard to soil properties and soil moisture.The current study describes the application of a combined two- and three-dimensional geoelectrical monitoring approach with daily measurements over two years (May 2021 – April 2023) in a forest ecosystem in Lower Franconia (northwestern Bavaria, Germany), which is strongly affected by climate change. Soil water content, soil matric potential, throughfall, and stem flow are also measured at the forest site as well as precipitation at an adjacent forest clearing.The seasonally (long-term) and precipitation-driven (short-term) temporal change of soil resistivity is correlated strongly with the measured soil water content and matric potential. The applied 3D-ERT approach also allowed a first three-dimensional monitoring of the subsurface below a European beech located in the middle of the measuring grid with a daily resolution. The corresponding results also provide first indications that besides soil moisture changes also chemical processes in the subsurface may influence temporal resistivity changes in the soil of forest sites.The results of this study show that daily 3D-ERT is very suitable for investigating small-scale as well as short- and long-term variations in soil moisture, which is becoming increasingly important for understanding the causal relationships considering tree mortality and the subsurface.

Assessing urban forest decline and predicting future expansion: a spatial analysis and modeling approach in João Pessoa City, Brazil

Assessing urban forest decline and predicting future expansion: a spatial analysis and modeling approach in João Pessoa City, Brazil

ЭКОЛОГИЯЛЫҚ БІЛІМ БЕРУДІ ДАМЫТУДЫҢ АЛҒЫ ШАРТТАРЫ

An important feature of our time is acute global regional and local environmentalcrisis . The destruction of the ozone layer in the Earth’s atmosphere, the Earth’s planetary climate change, progressive erosion and soil desertification, the decline of humid tropical forests, widespread pollution of the World Ocean and surface waters, the continuous increase in the population in the universe, the constant growth of poverty and hunger, many other global environmental manifestations are a reflection of the crisis of our time. And this is a clear proof that today’s people are in poor contact with nature. In order to avoid this environmental crisis, the prerequisites for the development of environmental education have been developed.

Summer heat induced the decline of Pinus taiwanensis forests at its southern limit in humid Subtropical China

Warming-induced aridity has caused forest decline and mortality for many sites with water-limiting conditions. However, equatorward rear-edge Pinus taiwanensis trees at the Daiyun Mountains in humid subtropical China are also suffering die-backs and decline, but the roles played by heat or drought stress still remain unclear. Here, we compared the tree-ring radial width, anatomical features, stable carbon isotope (δ13C) and intrinsic water use efficiency (iWUE) between die-back and healthy trees to elucidate potential causes driving the decline. Die-back trees showed sustained growth reductions and produced tracheids with thinner cell walls over the recent decade, indicative of reduced carbon assimilation. The climate response pattern and Vaganov-Shashkin (V-S) model indicated the critical role of summer (June-August) temperature in recent growth decline. Long-term higher wood δ13C and iWUE within die-back trees indicated that actual growth decline already started several decades earlier. This conservative growth strategy was at the cost of low efficiency of photosynthesis due to chronic stomatal closure. When the lethal heatwaves arrived, these weakened trees were not able to access sufficient carbonhydrates to maintain metabolism, causing a distinct decline and mortality. We concluded that recent decline in Pinus taiwanensis trees was mainly caused by long-term carbon starvation.

Mediterranean pine forest decline: A matter of root-associated microbiota and climate change

Forest ecosystems worldwide currently face worrying episodes of forest decline, which have boosted weakening and mortality of the trees. In the Mediterranean region, especially in the southeast Iberian Peninsula, Pinus sylvestris forests are severely affected by this phenomenon, and it has been commonly attributed to drought events. Remarkably, the role of root microbiota on pine decline has been overlooked and remains unclear. We therefore used metabarcoding to identify the belowground microbial communities of decline-affected and unaffected pine trees. Taxonomic composition of bacterial and fungal rhizosphere communities, and fungal populations dwelling in root endosphere showed different profiles depending on the health status of the trees. The root endosphere of asymptomatic trees was as strongly dominated by ‘Candidatus Phytoplasma pini’ as the root of decline-affected pines, accounting for >99 % of the total bacterial sequences in some samples. Notwithstanding, the titer of this phytopathogen was four-fold higher in symptomatic trees than in symptomless ones. Furthermore, the microbiota inhabiting the root endosphere of decline-affected trees assembled into a less complex and more modularized network. Thus, the observed changes in the microbial communities could be a cause or a consequence of forest decline phenomenon. Moreover, ‘Ca. Phytoplasma pini’ is positively correlated to Pinus sylvestris decline events, either as the primary cause of pine decline or as an opportunistic pathogen exacerbating the process once the tree has been weaken by other factors.

In Situ Rainwater Harvesting System Slows Forest Decline through Increasing Soil Water Content, Fine-Root Traits, and Plant Hydraulic Conductivity

Large-scale vegetation restoration campaigns have been implemented on the Chinese Loess Plateau, which have resulted in higher soil moisture deficits in this region. This, in turn, has hampered the healthy growth of planted trees, leading to a decline and, in severe cases, mortality of trees. Therefore, the rational regulation and utilization of rainwater, the primary water source in this region, may alleviate drought stress, ensuring the sustainability of the ecosystem. In this study, we investigated the impact of in situ rainwater collection and infiltration systems (IRCISs) on soil water, fine-root distribution, xylem vascular, and hydraulic conductivity characteristics in declining Robinia pseudoacacia forests. The results demonstrated that the application of an IRCIS can effectively increase plant available moisture content (0–5.0 m) of declining Robinia pseudoacacia forests. In particular, IRCIS treatment significantly increased xylem conduit diameter and plant hydraulic conductivity while substantially reducing the percentage loss of hydraulic conductivity in both roots and branches. Furthermore, IRCIS treatment significantly reduced the root biomass and distribution depth of Robinia pseudoacacia during both wet and dry years. This implies that IRCISs are beneficial for plant growth and survival. The findings of this study are significant for devising strategic methodologies for the planning and management of rainwater resources.

Contrasting patterns of water use efficiency and annual radial growth among European beech forests along the Italian peninsula

Tree mortality and forest dieback episodes are increasing due to drought and heat stress. Nevertheless, a comprehensive understanding of mechanisms enabling trees to withstand and survive droughts remains lacking. Our study investigated basal area increment (BAI), and δ13C-derived intrinsic water-use-efficiency (iWUE), to elucidate beech resilience across four healthy stands in Italy with varying climates and soil water availability. Additionally, fist-order autocorrelation (AR1) analysis was performed to detect early warning signals for potential tree dieback risks during extreme drought events. Results reveal a negative link between BAI and vapour pressure deficit (VPD), especially in southern latitudes. After the 2003 drought, BAI decreased at the northern site, with an increase in δ13C and iWUE, indicating conservative water-use. Conversely, the southern sites showed increased BAI and iWUE, likely influenced by rising CO2 and improved water availability. In contrast, the central site sustained higher transpiration rates due to higher soil water holding capacity (SWHC). Despite varied responses, most sites exhibited reduced resilience to future extreme events, indicated by increased AR1. Temperature significantly affected beech iWUE and BAI in northern Italy, while VPD strongly influenced the southern latitudes. The observed increase in BAI and iWUE in southern regions might be attributed to an acclimation response.

Beneficial effects of native broadleaved forests on canopy beetle diversity are not reduced by admixture of non‐native conifers

Abstract Biodiversity loss and vast forest diebacks due to climate change‐induced disturbances require adapted forest management strategies that reconcile economic interests and conservation. Tree species selection, including admixture of fast‐growing and drought‐tolerant non‐native species to native forests, is an increasingly considered approach. However, we lack data on how such mixtures affect native forest biodiversity, especially for the sparsely researched major above‐ground part of trees, the canopy. In 40 temperate forest plots in northwest Germany, we investigated how monocultures and admixtures of introduced fast‐growing conifers (native Norway spruce planted outside its natural range and non‐native Douglas fir) to native broadleaved European beech forests affect abundance, biomass, taxonomic and functional diversity and community composition of canopy beetles across trophic guilds. Diverse arthropod communities are vital contributors to forest health and resilience, and therefore valuable indicators to assess and evaluate forestry measures. Monospecific stands of non‐native Douglas fir reduced canopy beetle abundance and diversity compared to native European beech, exceeding the negative effects of Norway spruce. These effects were more pronounced for herbivorous beetles, while they were less strong for predators. Beetle communities in monospecific Norway spruce stands had low functional richness. European beech and mixtures with non‐native Douglas fir had high dissimilarity between local communities (turnover, i.e. beta diversity) and high total beetle diversity at landscape scale (gamma diversity). Mixtures generally mitigated the negative effects of introduced conifers, including shifts in species community composition compared to native European beech. Synthesis and applications: Monospecific stands of fast‐growing non‐native Douglas fir and native Norway spruce planted outside its natural occurrence showed undesirable effects such as low diversity and a shifted community composition of canopy beetles compared to native European beech. However, mixed stands mitigated negative effects and specifically admixed non‐native Douglas fir did not reduce species turnover and landscape‐scale beetle diversity. In line with recent studies on other forest taxa, we conclude that admixtures of introduced conifers to European beech forests, but not monospecific plantations, can potentially serve as a compromise between conservational and economic interests.

Elevation‐dependent patterns of borer‐mediated snow‐gum dieback are associated with subspecies' trait differences and environmental variation

AbstractSubalpine forests worldwide face the synergistic threats of global warming and increased biotic attack, and the collapse or transition of subalpine forests is predicted in south‐eastern Australia under future climates. The recent widespread dieback of subalpine snow‐gum forests due to increased activity of a native wood‐boring longicorn beetle, Phoracantha mastersii, suggests this process may already be underway. We investigated how variation in tree tissue traits and environmental conditions correlated with elevation‐dependent spatial patterns of forest mortality. We hypothesized that increased vulnerability of subalpine snow gums to wood‐borer‐mediated dieback at intermediate elevations was associated with poorly resolved differences in traits between montane (Eucalyptus pauciflora subsp. pauciflora) and subalpine (E. pauciflora subsp. niphophila) snow‐gum subspecies. We first sought to characterize variation and elevation‐dependent transitions in 20 structural and drought‐related functional traits among 120 healthy trees distributed along a 1000 m elevation transect that spanned the subspecies transition zone. Secondly, we surveyed 774 trees across 53 sites between 1280 and 1980 m a.s.l. to explore associations between borer‐damage severity, elevation, subspecies and a subset of traits that differed between subspecies. We observed evidence for both continuous trait variation in response to changing elevation (10/20 traits) and discrete shifts in mean trait values across the transition between subspecies distributions (5/20 traits). Increased borer‐damage severity across the montane‐to‐subalpine subspecies transition was correlated with lower bark thickness, whereas reduced borer damage at the highest elevations was associated with greater precipitation and lower temperatures. Our results suggest that due to possessing distinct traits associated with increased borer susceptibility, subalpine snow‐gum forests may be subject to an increased risk of severe borer‐mediated forest dieback under warmer and drier future climates. Identifying traits contributing to species' distribution limits and biotic‐agent vulnerability remains critical for predicting, monitoring and possibly mitigating forest and vegetation declines under future climates.

Oomycete communities are influenced by land use and disease status in Christmas tree production in Southern Québec, Canada

AbstractForests are threatened by many natural stressors intensified by climate change and anthropogenic activities, which tend to increase their susceptibility to pests and pathogens. Consequently, oomycete‐related forest decline or dieback cases are increasing in natural, urban, and agricultural landscapes. It is in this context that Christmas tree growers from Southern Québec, Canada, are experiencing root rot problems, with reported incidences up to 25%. In a previous study, seven Phytophthora spp. were associated with this root rot problem, but the overall diversity of oomycetes has not yet been investigated. Hence, in this study, we use a metabarcoding approach to provide an overview of the diversity, richness, and composition of the oomycete community in fir plantations compared to surrounding natural forests. We showed that the P. cryptogea cluster, P. europaea cluster, P. sansomeana, and P. chlamydospora cluster were significantly more abundant in soils collected from plantations under diseased trees and confirmed that the P. europaea cluster (including P. abietivora) was most frequently associated with trees showing Phytophthora root rot‐like symptoms. Finally, we report that land use (anthropogenic activities) shapes oomycete diversity, while plantations can act as a gateway for invading natural forests. In fact, the results presented here suggested that the P. europaea cluster might already have crossed this boundary and that other species might follow, advocating the importance of improved surveillance of oomycete diversity in various environments.

Spatio-Temporal Patterns of Land Use and Cover Change in the Lancang–Mekong River Basin during 2000–2020

Exploring the mechanisms that drive land use and cover change (LUCC) is essential for informing the formulation and implementation of effective policies aimed at optimizing land use patterns. In this study, we examined the spatial and temporal patterns of LUCC within the Lancang–Mekong River Basin (LMRB) using Globeland30 data for the years 2000, 2010, and 2020. Firstly, we analyzed the quantitative characteristics of LUCC within the LMRB in terms of the value of change and rate of change. Additionally, we investigated the converting characteristics of LUCC within the LMRB by employing land use transition matrices and land use transition probability matrices. Furthermore, we depicted the spatial distribution of LUCC within the LMRB through land use mapping and statistical analysis. The results indicate a substantial decline in forests, coupled with a notable expansion in cultivated land. Given the vital role of forests as carbon sinks, reforestation can enhance ecological services and address challenges related to climate change. Converting cultivated land to forests is an effective human intervention promoting forest transition. This study applies binary logistic models to explore the mechanisms that influence the conversion from cultivated land to forests. The results reveal that slopes ranging from 5° to 15° have the lowest probability of conversion, whereas distances between the cultivated land and the nearest tourist attraction ranging from 9 km to 18 km have the highest probability. Moreover, the conversion process is positively associated with traffic conditions and significantly influenced by human interventions. Within the study area, China, Laos, and Myanmar show a tendency to convert cultivated land into natural LULC types, while Cambodia, Thailand, and Vietnam tend to encroach on cultivated land and expand artificial surfaces. Promoting ecological restoration in the LMRB requires cooperation among these countries.

Unpacking the point of no return under drought in poplar: insight from stem diameter variation.

A specific, robust threshold for drought-induced tree mortality is needed to improve the prediction of forest dieback. Here, we tested the relevance of continuous measurements of stem diameter variations for identifying such a threshold, their relationship with hydraulic and cellular damage mechanisms, and the influence of growth conditions on these relationships. Poplar saplings were grown under well-watered, water-limited, or light-limited conditions and then submitted to a drought followed by rewatering. Stem diameter was continuously measured to investigate two parameters: the percentage loss of diameter (PLD) and the percentage of diameter recovery (DR) following rewatering. Water potentials, stomatal conductance, embolism, and electrolyte leakage were also measured, and light microscopy allowed investigating cell collapse induced by drought. The water release observed through loss of diameter occurred throughout the drought, regardless of growth conditions. Poplars did not recover from drought when PLD reached a threshold and this differed according to growth conditions but remained linked to cell resistance to damage and collapse. Our findings shed new light on the mechanisms of drought-induced tree mortality and indicate that PLD could be a relevant indicator of drought-induced tree mortality, regardless of the growth conditions.

Xylem plasticity of root, stem, and branch in Cunninghamia lanceolata under drought stress: implications for whole-plant hydraulic integrity.

A better understanding of xylem hydraulic characteristics in trees is critical to elucidate the mechanisms of forest decline and tree mortality from water deficit. As well as temperate forests and forests growing in arid regions, subtropical and tropical forests are also predicted to experience an increased frequency and intensity of climate change-induced drought in the near future. In this study, 1-year-old Cunninghamia lanceolata seedlings (a typical subtropical species in southern China) were selected for a continuous controlled drought pot experiment of 45 days duration. The experimental treatments were non-drought (control), light drought, moderate drought and severe drought stress, which were 80%, 60%, 50%, and 40%, respectively of soil field maximum moisture capacity. The hydraulic conductivity, specific conductivity and water potential of roots, stems, and branches of C. lanceolata all decreased with the prolonging of drought in the different drought intensities. The relative decrease in these hydraulic values were greater in roots than in stems and branches, indicating that roots are more sensitive to drought. Root tracheid diameters normally reduce to ensure security of water transport with prolonged drought, whilst the tracheid diameters of stems and branches expand initially to ensure water transport and then decrease to reduce the risk of embolism with continuing drought duration. The pit membrane diameter of roots, stems and branches generally increased to different extents during the 15-45 days drought duration, which is conducive to enhanced radial water transport ability. The tracheid density and pit density of stems generally decreased during drought stress, which decreased water transport efficiency and increased embolism occurrence. Correlation analysis indicated that anatomical plasticity greatly influenced the hydraulic properties, whilst the relationships varied among different organs. In roots, tracheid diameter decreased and tracheid density increased to enhance water transport security; stems and branches may increase tracheid diameter and pit membrane diameter to increase hydraulic conductivity ability, but may increase the occurrence of xylem embolism. In summary, under drought stress, the xylem anatomical characteristics of C. lanceolata organs were highly plastic to regulate water transport vertically and radially to maintain the trade-off between hydraulic conductivity efficiency and safety.

Abiotic factors impact on oak forest decline in Lorestan Province, Western Iran

The Zagros oak forests in Iran are facing a concerning decline due to prolonged and severe drought conditions over several decades, compounded by the simultaneous impact of temperature on oak populations. This study in oak woodlands of central Zagros forests in Lorestan province analyzed abiotic factors such as climate properties, topographic features, land use, and soil properties from 1958 to 2022. We found that higher elevation areas with steeper slopes and diverse topography show significant potential for enhancing oak tree resilience in the face of climate change. Additionally, traditional land use practices like livestock keeping and dryland farming contribute to a widespread decline in oak populations. Preserving forest biodiversity and ensuring ecological sustainability requires immediate attention. Implementing effective land-use management strategies, such as protecting and regulating human-forest interaction, and considering meteorological factors to address this issue is crucial. Collaborative efforts from stakeholders, policymakers, and local communities are essential to oppose destructive suburban sprawl and other developments. Sustainable forestry practices should be implemented to improve the living standards of local communities that rely on forests and traditional livestock keeping, offer forestry-related jobs, and ensure social security. Such efforts are necessary to promote conservation awareness and sustainable practices, safeguarding this unique and vital ecosystem for future generations.

Relationship between Tree Girth and Forest Dieback Severity in Horton Plains National Park, Sri Lanka

Forest dieback changes the physiognomy, structure and floristic composition of montane forests leading to deterioration of ecosystem services. Although research has been conducted to investigate the etiology of forest dieback at Horton Plains National Park (HPNP), a direct cause for this phenomenon is yet to be identified. We investigated the relationship of plant maturity with forest dieback in montane forest species at HPNP. Two sites were selected considering the dieback percentages: less than 25% crown dieback as the healthy site and more than 75% crown dieback as the severe forest dieback site. The percentage crown dieback and girth at breast height was recorded in all individuals>10 cm in both plots. The mean GBH varied significantly among different crown dieback categories in five tree species in the healthy site and four tree species in the severe forest dieback site. In the healthy site, the mean GBH of healthy Cinnamomum ovalifolium trees was lower than that of dead trees while in the severe dieback site, it was higher for the severe crown dieback category than the healthy and rare dieback categories. In the severe dieback site, the mean GBH of healthy Symplocos obtusa trees was lower than that of the medium crown dieback category, while the mean GBH of dead Eurya chinensis trees was higher than that of healthy and rare crown dieback categories, in the severe dieback site. Furthermore, low crown dieback percentages were recorded in Syzygium rotundifolium, Vaccinium leschenaulti, and Litsea ovalifolia with the low mean GBH. A lower mean GBH was recorded for dead individuals of Symplocos cordifolia than healthy individuals. More research must be conducted to understand the relationships between forest dieback and site-specific factors to ensure the success of conservation efforts in tropical montane forests at HPNP.
 Keywords: Forest dieback, GBH, Plant maturity, Tropical montane forests

Arriving at a tipping point for worldwide forest decline due to accelerating climatic change

The 2023–2024 El Niño is inducing an acceleration of global warming that is likely to far exceed 1.5 °C. The Boreal summer of 2023 provided numerous examples of catastrophic forest fires (e.g., >18 million hectares of forest burned in Canada, making the Canadian forest a clear carbon source rather than a carbon sink), a trend that has been accompanied by worldwide examples of unusual tree mortality linked to hotter droughts. It is reasonable to expect that the warming induced by El Niño could push forests in several parts of the world over a tipping point, where they will hardly be able to recover their original state. It is therefore necessary to address the meaning, realistically, of sustainable forest management in the era of accelerated climatic change. The ultimate goal of the broadly accepted silvicultural practice of maintaining forests in a state that resembles what we recognize as temperate or boreal forests is becoming more of an idealistic dream rather than an attainable goal. Thus, the time has arrived to discuss painful forest management decisions, such as anticipated thinning to reduce water competition and the gradual replacement of native local forest populations with more drought-resistant provenances and species.