The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous forest types. We reveal a bimodal distribution of forest leaf types across temperate regions of the Northern Hemisphere that cannot be explained by the environment alone, suggesting signatures of alternative forest states. Moreover, we empirically demonstrate the existence of positive feedbacks in tree growth, recruitment and mortality, with trees having 4–43% higher growth rates, 14–17% higher survival rates and 4–7 times higher recruitment rates when they are surrounded by trees of their own leaf type. Simulations show that the observed positive feedbacks are necessary and sufficient to generate alternative forest states, which also lead to dependency on history (hysteresis) during ecosystem transition from evergreen to deciduous forests and vice versa. We identify hotspots of bistable forest types in evergreen-deciduous ecotones, which are likely driven by soil-related positive feedbacks. These findings are integral to predicting the distribution of forest biomes, and aid to our understanding of biodiversity, carbon turnover, and terrestrial climate feedbacks.
Tag: forest conservation
Forest structure and composition under contrasting precipitation regimes in the high mountains, Western Nepal
The high mountains stretch over 20.4% of Nepal’s land surface with diverse climatic conditions and associated vegetation types. An understanding of tree species and forest structural pattern variations across different climatic regions is crucial for mountain ecology. This study strived to carry out a comparative evaluation of species diversity, main stand variables, and canopy cover of forests with contrasting precipitation conditions in the Annapurna range. Firstly, climate data provided by CHELSA version 1.2, were used to identify distinct precipitation regimes. Lamjung and Mustang were selected as two contrasting precipitation regions, and have average annual precipitation of 2965 mm and 723 mm, respectively. Stratified random sampling was used to study 16 plots, each measuring 500 m2 and near the tree line at an elevation range of 3000 to 4000 m across different precipitation conditions. In total, 870 trees were identified and measured. Five hemispherical photos using a fisheye lens were taken in each plot for recording and analyzing canopy cover. Margalef’s index was used to measure species richness, while two diversity indices: the Shannon–Wiener Index and Simpson Index were used for species diversity. Dominant tree species in both study regions were identified through the Important Value Index (IVI). The Wilcoxon rank-sum test was employed to determine the differences in forest structure and composition variables between the two precipitation regimes. In total, 13 species were recorded with broadleaved species predominating in the high precipitation region and coniferous species in the low precipitation region. Higher species richness and species diversity were recorded in the low precipitation region, whereas the main stand variables: basal area and stem density were found to be higher in the high precipitation region. Overall, an inverse J-shaped diameter distribution was found in both precipitation regions signifying uneven-aged forest. A higher proportion of leaning and buttressed trees were recorded in the high precipitation region. However, similar forest canopy cover conditions (>90%) were observed in both study regions. The findings of this research provide a comprehensive narrative of tree species and forest structure across distinct precipitation regimes, which can be crucial to administrators and local people for the sustainable management of resources in this complex region.
Intensity and embeddedness: Two dimensions of equity approaches in multi-stakeholder forums
This occasional paper presents a new approach to examining how multi-stakeholder forums (MSFs) on land use and land-use change address equity. Based on a review of cases in the scholarly literature, we engage with MSFs from two key characteristics: the degree to which an MSF includes local peoples as part of a forest-landscape solution (its intensity), and the degree to which an MSF and/or its goals or objectives are embedded or entangled in wider societal or governmental programs and processes (its embeddedness).
Multi-stakeholder forums (MSFs) have been positioned as a transformative solution for more sustainable decision making in forestry, land use, and climate change interventions. Yet, we propose that an MSF’s resilience and potential to promote equity is impeded if local peoples are not regarded as key partners rather than ‘beneficiaries’, and if the forum and/or its outcomes are not meaningfully institutionalized.
Intensity and embeddedness are useful analytical tools that go beyond typologies that identify characteristics found in successful MSFs. They are helpful in terms of explaining how different approaches across different contexts function and add nuance to simplified dichotomies. The analytical application of intensity and embeddedness to the analysis of MSFs permits new insights as they describe cases and explain how they differ in terms of equity.
Remotely sensed tree canopy cover-based indicators for monitoring global sustainability and environmental initiatives
With the intensifying challenges of global environmental change, sustainability, and biodiversity conservation, the monitoring of the world’s remaining forests has become more important than ever. Today, Earth observation technologies, particularly remote sensing, are at the forefront of forest cover monitoring worldwide. Given the current conceptual understanding of what a forest is, canopy cover threshold values are used to map forest cover from remote sensing imagery and produce categorical data products such as forest/non-forest (F/NF) maps. However, multi-temporal categorical map products have important limitations because they inadequately represent the actual status of forest landscapes and the trajectories of forest cover changes as a result of the thresholding effect. Here, we examined the potential of using remotely sensed tree canopy cover (TCC) datasets, which are continuous data products, to complement F/NF maps for forest cover monitoring. We developed a conceptual analytical framework for forest cover monitoring using both types of data products and applied it to the forests of Southeast Asia. We conclude that TCC datasets and the statistics derived from them can be used to complement the information provided by categorical F/NF maps. TCC-based indicators (i.e. losses, gains, and net changes) can help in monitoring not only deforestation but also forest degradation and forest cover enhancement, all of which are highly relevant to the 2030 Agenda for Sustainable Development and other global forest cover monitoring-related initiatives. We recommend that future research should focus on the production, application, and evaluation of TCC datasets to advance the current understanding of how accurately these products can capture changes in forest landscapes across space and time.
Evaluating the Impact of REDD+ Interventions on Household Forest Revenue in Peru
REDD+ was conceived as a system of incentives for reducing emissions from deforestation and degradation. While this could include many different types of interventions to reduce deforestation and degradation, a consensus has emerged that they should safeguard and “do no harm” to the forest-based livelihoods of local people. Many REDD+ projects have been designed to incentivize forest conservation and support local livelihoods by promoting sustainable use of the forest, hence increasing the revenues earned by local households from forest products. We examine two such projects in the Peruvian Amazon, using panel survey data from over 400 households gathered in 2011 and 2014. In the 3 years between surveys, we observed a severe decline in forest revenue. However, by using a BACI study design and matching, we show that this decrease was not caused by the REDD+ interventions. Thus, REDD+ “did no harm” to local people, at least in terms of forest revenues in the early phases of these two projects in the Peruvian Amazon.
More people, more trees: A reversal of deforestation trends in Southern Ethiopia
Despite global commitments to forest restoration, evidence of the pathways through which restoration creates social and ecological benefits remains limited. The objective of this paper is to provide empirical evidence to generate insights on the relationship between forest cover change and key provisioning ecosystem services and reforestation pathways. In Southern Ethiopia, three zones along a gradient of decreasing land cover complexity and tree cover were examined. The land cover change was assessed using satellite remote sensing and complemented ground‐based tree inventory. Perceptions of land cover and ecosystem services change and farmer responses were evaluated through three Participatory Rural Appraisals and eight Focus Group Discussions. Since the 1970s, a landscape shift from a forest‐grassland to a cropland mosaic was associated with increased food production, improved food security, and higher incomes. However, this shift also coincided with reductions in livestock, construction materials, fuelwood and water availability, prompting reforestation efforts designed to recover some of these lost ecosystem services. In particular, some households established Eucalyptus woodlots and encouraged natural regeneration. Natural trees, Eucalyptus woodlots, Ensete plantations (a type of plantain), and grasslands were positively associated with homestead proximity; thus, homestead establishment resulting from population increase in this predominately agricultural landscape appeared to foster a viable forest restoration pathway—that is, ‘more people, more trees’. This is a reforestation pathway not previously described in the literature. A return to a more diverse agricultural landscape mosaic provided more secure and diversified income sources along with better provisioning of construction materials, fuelwood, and higher livestock numbers.
Trees, tree genetic diversity and the livelihoods of rural communities in the tropics
This study, prepared within the ambit of The State of the World’s Forest Genetic Resources, reviews what is known about the value of trees for tropical rural communities. It focuses on non-timber products harvested from trees in natural and managed forests and woodlands, the various products and services obtained from trees planted or retained in agroforestry systems, and the commercial products of tree commodity crops. The role of intra-specific genetic variation in determining the value of trees in supporting livelihoods is discussed in each of the three contexts. The study also identifies specific points that should be given particular attention in the future to better support tree-based livelihoods of rural communities in the tropics.