African rainforests: past, present and future

In recent decades, there has been a surge of interest in tropical forests, as there is increased appreciation of the rich biodiversity they host and the many roles they play in the functioning of the Earth system at local, regional and global scales. Of the world’s major tropical forest regions, most research and policy attention has focused on the Amazon region, the world’s largest tropical forest bloc, and to a lesser extent on South East Asia, the third largest tropical forest region. By contrast, the world’s second largest tropical forest region, the tropical forests of Central and West Africa (termed the Guineo-Congolian region) have been relatively neglected. This has been for a number of reasons, including challenging and fragmented politics, civil conflicts and logistical as well as infrastructure challenges. Nevertheless, there is an extensive amount of research activity in the African rainforest zone that has rarely been compiled in a single interdisciplinary volume. This review paper synthesizes the insights emerging from the theme issue on ‘African rainforests: past, present and future’ of Philosophical Transactions of the Royal Society.JRC.H.5-Land Resources Managemen

The past, present and future of Africa's rainforests

The Africanwet tropics contain the second largest area of tropical rainforest in the world (second only toAmazonia), accounting for roughly 30% of global rainforest cover, the lush green heart of an otherwise generally dry continent. These rainforests have global significance and value as reservoirs of biodiversity, as stores and sinks of atmospheric carbon, as regulators of flow of mighty rivers, as sources of moisture to the atmosphere and engines of the global atmospheric circulation, as a key component of the Earth system and its biogeochemical cycles, and as providers of resources and ecosystem services to local communities and the region’s nations. They also have a unique and particular history of changes in climate and human pressure, and face a range of contemporary pressures. Over the twenty-first century, the African rainforest realmhas the potential to witness massive change, both through an expansion of deforestation, hunting and logging, and through the effects of global climate change. This Theme Issue presents a multidisciplinary perspective on the nature and ecology of the African rainforest biome, and examines the current pressures and future threats to this biome. Compared with the other major rainforest regions, Amazonia and Southeast Asia, the African rainforest realm remains understudied, and in particular there have been very few attempts at interdisciplinary synthesis. This Theme Issue is an attempt to address this deficit, and explores what we know about the African rainforests and the threats they face, and what we need to know is this century of rapid change. In some ways, this can be viewed as a complement to similar Theme Issues of this journal focused on the rainforests of Amazonia [1,2] and Southeast Asia [3].JRC.H.5-Land Resources Managemen

Abundance and Diversity of Trees Species Under Different Land Uses in the Sudan Savannah Ecological Zone of Ghana, West Africa

Knowledge on tree species abundance and diversity is critical for sustainable land management and biodiversity conservation. The aim of the study was to assess tree species abundance and diversity across different land uses and sites in the Sudan savannah ecological zone of Ghana, a total of 64 plots of 3600 m2 (60 m x 60 m) were laid out in three land use types (Forest reserve, cropland and rangeland) in four sites (Bawku, Binduri, Garu and Pusiga). All standing trees and shrubs species encountered in the setting plot were recorded including dendrometry parameters. Alpha diversity was measured using Simpson, Shannon-Wiener and Evenness indices whereas similarity in species composition between land use types and sites were measured using Sorenson’s index. The results showed that there were more species in the lower diameter classes (0 to 20 cm) than the higher diameter classes (>20 cm). the greatest value of tree diversity was recorded in forest land in the four sites compared to the other land use types. The highest similarity (53%) in tree species composition was recorded between cropland in Binduri and Garu. the current study revealed that forest land recorded the highest value of tree species richness in each site compared to the other two land use types (cropland and rangeland) in the same site

Termites have wider thermal limits to cope with environmental conditions in savannas

1. The most diverse and abundant family of termites, the Termitidae, evolved in African tropical forests. They have since colonised grassy biomes such as savannas. These open environments have more extreme conditions than tropical forests, notably wider extremes of temperature and lower precipitation levels and greater temporal fluctuations (of both annual and diurnal variation). These conditions are challenging for soft-bodied ectotherms, such as termites, to survive in, let alone become as ecologically dominant as termites have. 2. Here, we quantified termite thermal limits to test the hypothesis that these physiological limits are wider in savanna termite species to facilitate their existence in savanna environments. 3. We sampled termites directly from mound structures, across an environmental gradient in Ghana, ranging from wet tropical forest through to savanna. At each location, we quantified both the Critical Thermal Maxima (CTmax) and the Critical Thermal Minima (CTmin) of all the most abundant mound-building Termitidae species in the study areas. We modelled the thermal limits in two separate mixed-effects models against canopy cover at the mound, temperature and rainfall, as fixed effects, with sampling location as a random intercept. 4. For both CTmax and CTmin, savanna species had significantly more extreme thermal limits than forest species. Between and within environments, areas with higher amounts of canopy cover were significantly associated with lower CTmax values of the termite colonies. CTmin was significantly positively correlated with rainfall. Temperature was retained in both models; however, it did not have a significant relationship in either. Sampling location explained a large proportion of the residual variation, suggesting there are other environmental factors that could influence termite thermal limits. 5. Our results suggest that savanna termite species have wider thermal limits than forest species. These physiological differences, in conjunction with other behavioural adaptations, are likely to have enabled termites to cope with the more extreme environmental conditions found in savanna environments and facilitated their expansion into open tropical environments.Royal Society-DFID/FCDO Capacity Building Initiative; NERC ACCE DTP.http://wileyonlinelibrary.com/journal/janeZoology and Entomolog

Variability in modern pollen rain from moist and wet tropical forest plots in Ghana, West Africa

How pollen moves within and between ecosystems affects factors such as the genetic structure of populations, how resilient they are to environmental change, and the amount and nature of pollen preserved in the sedimentary record. We set artificial pollen traps in two 100 m by 100 m vegetation plots, one in a wet evergreen forest, and one in a moist semi-deciduous forest in Ghana, West Africa. Five traps from each plot were counted annually from 2011 to 2014, to examine spatial and temporal variation in the pollen rain of the most abundant taxa shared between pollen and vegetation assemblages. Samples from the wet evergreen plot exhibited high variability within years, with the dominant pollen types changing between samples, and many pollen taxa being over-represented relative to their parent plant abundance in some traps whilst being entirely absent from others. The most abundant plant taxa of the wet evergreen plot (Drypetes and Cynometra) do, however, constitute major components of the pollen rain. There is less variation between samples from the moist semi-deciduous plot spatially, as it is dominated by Celtis, which typically comprises >70% of the pollen assemblages. We conclude that pollen rain in these tropical ecosystems is highly heterogeneous, and suggest that pollen assemblages obtained by trapping are susceptible to small-scale variations in forest structure. Conversely, this may mean that current recommendations of more than three years of trapping in tropical systems may be too high, and that space could substitute for time in modern tropical pollen trapping

Extending the baseline of tropical dry forest loss in Ghana (1984–2015) reveals drivers of major deforestation inside a protected area

Tropical dry forests experience the highest deforestation rates on Earth, with major implications for the biodiversity of these ecosystems, as well as for its human occupants. Global remote sensing based forest cover data (2000 − 2012) point to the rapid loss of tropical dry forest in South America and Africa, also, if not foremost, inside formally protected areas. Here, we significantly extend the baseline of tropical dry forest loss inside a protected area in Ghana using a generalizable change detection technique. The forest cover change detection is based on the normalized difference vegetation index (NDVI) derived from historical Landsat data (1984–2015). Field measurements were carried out in dry semi-deciduous forest and in the adjacent savanna and woodland. Estimates of the canopy area index and above ground woody biomass were related to NDVI derived from Landsat 8 data. The change detection indicated significant NDVI decrease in a large area initially covered by tropical dry forest, associated with deforestation. The peak in deforestation was found to have occurred between 1990 and 2002, hereafter, the conservation status of the area was improved. A combination of remote sensing data corroborated by secondary data sources provides evidence for the almost complete clearance of a tropical dry forest inside a strictly protected area, attributable to logging and land clearing for arable farming. The NDVI change detection also revealed NDVI increase in the adjacent woodlands from 2002 to 2015, demonstrating woody encroachment. Historical fire data from the MODIS burned area product indicate that the deforested area experienced a high frequency of anthropogenic burning since 2004, which may have caused further degradation and largely prevents forest regeneration. The results show the ongoing destruction of tropical ecosystems even within ostensibly protected areas and ask for the revision of protection and management strategies of such areas

Deforestation in forest-savannah transition zone of Ghana: Boabeng-Fiema monkey sanctuary

Forests provide many resources, ecosystem services and absorb carbon dioxide, which helps in climate regulation. In spite of the enormous benefits of forests, the issue of deforestation is still ongoing. There has been a continuous decline in forests globally and the forest area of Boabeng Fiema Monkey Sanctuary (BFMS) in Ghana is facing a similar threat. The aim of the study is to determine the different forest cover types and changes in the forest of BFMS. Satellite images for the years 1992, 1998, 2004, 2010, 2016 and 2018 were downloaded. Unsupervised and supervised classification were performed to determine the different forest cover types and remote sensing software was used to detect the changes in the forest cover. The forest cover was classified into six classes; closed forest, open forest, savannah woodland, savannah, farmlands and built-up area. Available data suggests that between 1992 and 2018, closed forest decreased by 242.19ha, open forest increased by 122.85 ha, savannah woodland increased by 7.47ha, savannah increased by 6.48 ha, farmland increased by 39.39ha and built-up area increased by 65.7ha. The changes in closed forest, open forest, farmland and built-up were all significant. Decreasing forest cover of BFMS is a threat to sustainable ecotourism since the forest serves as a habitat and food source to the monkeys. This research serves as guide to other researches aiming at determining forest cover changes in forest-savannah transition zones. In addition, the results have produced an inventory of the forest, which will help forest resource managers sustainably manage the forest

The influence of taxonomy and environment on leaf trait variation along tropical abiotic gradients

Deconstructing functional trait variation and co-variation across a wide range of environmental conditions is necessary to increase the mechanistic understanding of community assembly processes and improve current parameterization of dynamic vegetation models. Here, we present a study that deconstructs leaf trait variation and co-variation into within-species, taxonomic-, and plot-environment components along three tropical environmental gradients in Peru, Brazil, and Ghana. To do so, we measured photosynthetic, chemical, and structural leaf traits using a standardized sampling protocol for more than 1,000 individuals belonging to 367 species. Variation associated with the taxonomic component (species + genus + family) for most traits was relatively consistent across environmental gradients, but within-species variation and plot-environment variation was strongly dependent on the environmental gradient. Trait-trait co-variation was strongly linked to the environmental gradient where traits were measured, although some traits had consistent co-variation components irrespective of gradient. Our results demonstrate that filtering along these tropical gradients is mostly expressed through trait taxonomic variation, but that trait co-variation is strongly dependent on the local environment, and thus global trait co-variation relationships might not always apply at smaller scales and may quickly change under future climate scenarios.Fil: Oliveras, Imma. University of Oxford; Reino UnidoFil: Bentley, Lisa. Sonoma State University; Estados UnidosFil: Fyllas, Nikolaos M.. University Of The Aegean; GreciaFil: Gvozdevaite, Agne. University of Oxford; Reino UnidoFil: Shenkin, Alexander Frederick. University of Oxford; Reino UnidoFil: Peprah, Theresa. Forestry Research Institute Of Ghana; GhanaFil: Morandi, Paulo. Universidade Federal do Mato Grosso do Sul; BrasilFil: Peixoto, Karine Silva. Universidade Federal do Mato Grosso do Sul; BrasilFil: Boakye, Mickey. Forestry Research Institute Of Ghana; GhanaFil: Adu-Bredu, Stephen. Csir - Forestry Research Institute Of Ghana; GhanaFil: Schwantes Marimon, Beatriz. Universidade Do Estado de Mato Grosso; BrasilFil: Marimon Junior, Ben Hur. Universidade Do Estado de Mato Grosso; BrasilFil: Salinas, Norma. Pontificia Universidad Católica de Perú; PerúFil: Martin, Roberta. Arizona State University; Estados UnidosFil: Asner, Gregory. Arizona State University; Estados UnidosFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Enquist, Brian J.. University of Arizona; Estados UnidosFil: Malhi, Yadvinder. University of Oxford; Reino Unid

The modern pollen-vegetation relationship of a tropical forest-savannah mosaic landscape, Ghana, West Africa

Transitions between forest and savannah vegetation types in fossil pollen records are often poorly understood due to over-production by taxa such as Poaceae and a lack of modern pollen-vegetation studies. Here, modern pollen assemblages from within a forest-savannah transition in West Africa are presented and compared, their characteristic taxa discussed, and implications for the fossil record considered. Fifteen artificial pollen traps were deployed for 1 year, to collect pollen rain from three vegetation plots within the forest-savannah transition in Ghana. High percentages of Poaceae and Melastomataceae/Combretaceae were recorded in all three plots. Erythrophleum suaveolens characterised the forest plot, Manilkara obovata the transition plot and Terminalia the savannah plot. The results indicate that Poaceae pollen influx rates provide the best representation of the forest-savannah gradient, and that a Poaceae abundance of >40% should be considered as indicative of savannah-type vegetation in the fossil record