The Tropical Andes are characterized by a high level of endemism and plant species richness but are under pressure from human activities. We present the first regional conservation assessment of upper montane tree species in this region. We identified 3,750 tree species as occurring in this region, of which 917 were excluded because of a lack of data on their distribution. We identified a subset of 129 taxa that were restricted to higher elevations (> 1,500 m) but occurred in more than one country, thus excluding local endemics evaluated in previous national assessments. Distribution maps were created for each of these selected species, and extinction risk was assessed according to the IUCN Red List categories and criteria (version 3.1), drawing on expert knowledge elicited from a regional network of specialists. We assessed one species, Polylepis microphylla, as Critically Endangered, 47 species as Endangered and 28 as Vulnerable. Overall, 60% of the species evaluated were categorized as threatened, or 73% if national endemics are included. It is recommended that extinction risk assessments for tree species be used to inform the development of conservation strategies in the region, to avoid further loss of this important element of biodiversity.

Although trees have high economic, cultural and ecological value, increasing numbers of species are potentially at risk of extinction because of forest loss and degradation as a result of human activities, including overharvesting, fire and grazing. Emerging threats include climate change and its interaction with the spread of pests and diseases. The impact of such threats on the conservation status of trees is poorly understood. Here we highlight the need to conduct a comprehensive conservation assessment of the world's tree species, building on previous assessments undertaken for the IUCN Red List. We suggest that recent developments in plant systematics, online databases, remote sensing data and associated analytical tools offer an unprecedented opportunity to conduct such an assessment. We provide an overview of how a Global Tree Assessment could be achieved in practice, through participative, open-access approaches to data sharing and evaluation.

With 10% of trees (> 8,000 species) threatened with extinction there is an urgent need for botanical gardens to protect threatened trees in dedicated conservation collections. Species conservation is mentioned in the mission statements of most major botanical gardens, yet the actual conservation value of existing ex situ tree collections is low. We conducted interviews with members of the botanical garden community and organized a symposium at the 5th Global Botanic Gardens Congress to identify challenges and collect recommendations to improve living ex situ tree collections. We summarize and evaluate this information to facilitate gardens becoming more effective agents for global tree conservation. Experts agree that gardens offer valuable strengths and assets for tree conservation. Some challenges exist, however, including a lack of strategic conservation focus, collection management limitations, gaps in fundamental biological information for trees, and a lack of global coordination. Solutions are offered to facilitate gardens and arboreta of all sizes to participate more effectively in tree conservation. Prioritizing genetically diverse tree collections, participating in conservation networks, developing tree-specific conservation models and guidelines, and strengthening tree science research efforts are a few examples. Most importantly, a more coordinated global effort is needed to fill knowledge gaps, share information, and build conservation capacity in biodiversity hotspots to prevent the loss of tree species.

Ecological restoration of trees is often constrained by limited knowledge of the biology, propagation and management requirements of individual species. Consequently, restoration initiatives rarely incorporate less well-known species or those that are difficult to source and grow. We describe challenges associated with the restoration of threatened trees in the Araucaria Forest of southern Brazil, and analyse the effectiveness of methods used to define target species, identify seed sources and generate information on the phenology of rare or threatened tree species. A review of secondary data identified 71 rare or threatened taxa as targets for seed collection. We then surveyed 68.7 km of trails in 26 forest remnants, identifying and mapping 1,027 seed-producing trees of 38 species. Surveys confirmed the scarcity of several tree species (including seven species with an abundance of <0.04 individuals per km), and nine species showed no signs of fruiting during 3 years of phenological monitoring. These findings, together with limited knowledge and application of optimal seed collection methods, are significant factors impeding the recovery of these species within their natural habitat. Wider application of the results of this case study could support restoration of the Araucaria Forest with seedlings from a wider diversity of species.

Wild tree resins generate billions of dollars in revenue annually but many species face extinction. The lansan tree Protium attenuatum has disappeared across most of its range as a result of overexploitation for its valuable oleoresin, which is used as incense. This study in Saint Lucia aimed to determine whether lansan resin could be harvested sustainably. Over 34 months, 298 trees were tapped using 10 experimental methods, and compared with 74 controls. Significantly more resin was produced by tapping the same trees repeatedly, tapping trees with a wider girth, cutting the same part of the trunk repeatedly, and, in particular, spraying diluted sulphuric acid on the cut. Applying 5 and 30% sulphuric acid boosted yields by 58 and 134%, respectively, without negative impacts on tree growth, condition or mortality. In contrast, traditional methods used by local tappers were destructive, causing greater decay and infection, slower growth rates and increased mortality. Results show tappers can obtain more resin and maintain healthy populations by tapping mature trees of ≥ 20 cm diameter at breast height, using only one shallow cut per tree (refreshed every 2 weeks) and applying weak sulphuric acid solution. A blind survey found consumers could not distinguish between incense produced with or without this stimulant. A national management plan has been devised whereby tappers will be licensed and trained in the optimal method and granted their own forest coupes to manage under Forestry Department supervision. The methods and findings may guide the sustainable use and conservation of other resin-producing trees.

Apes, like many frugivorous animals, are crucial allies for the reproduction of several fruiting tree species. Almost all apes, however, including bonobos Pan paniscus, are threatened with extinction. How will this affect tree conservation? How can plants that are adapted to seed dispersal by apes reproduce without their dispersal vectors? At LuiKotale, in an evergreen tropical forest of the Democratic Republic of Congo, the recruitment of 22 plant species in the absence of seed dispersal was investigated under the parental canopy, where a proportion of seeds fall without horizontal dissemination. Most bonobo-dispersed plant species (95% of 19 species) were unable to self-recruit under the canopy. As 40% of the tree species (65% of trees) at LuiKotale are dispersed by bonobos there is a risk of ecosystem decay and simplification (reduced biodiversity) if Pan paniscus disappears from its natural range. The extinction of other apes from their forests could have similar consequences. The conservation of tree species, therefore, must encompass conservation of pollinators, seed dispersal vectors and other species that provide ecological services to the trees and other fruiting plants.

Land-use change can have negative effects on threatened species by modifying their habitat and population dynamics. The habitat of the Endangered Patagonian cypress Fitzroya cupressoides (Mol.) Johnst. (Cupressaceae), a conifer endemic to the temperate forests of southern Chile and Argentina, has been transformed by land-use change and overexploitation. The impact of land-use change on the spatial pattern of F. cupressoides habitat from 1999 to 2011 was evaluated at the landscape level, using satellite images. Additionally, eight 20 × 25 m plots were established in four populations to assess their status. In each plot the density of F. cupressoides and the species richness of the associated plant communities were recorded and analysed, together with spatial patterns at the population and community levels. The loss of potential F. cupressoides habitat was 46% from 1999 to 2011 (38–100% for the four populations). The density of F. cupressoides was lowest in smaller habitat patches, where the number of plant species was higher and the matrix dominated by anthropogenic land-use. Land-use change was associated with a loss of potential habitat for F. cupressoides, and differences in the spatial patterns of habitat influenced the composition of remaining populations and communities. A landscape approach is recommended as a conservation planning strategy for F. cupressoides.