scholarly journals Response of African humid tropical forests to recent rainfall anomalies

2013 ◽  
Vol 368 (1625) ◽  
pp. 20120306 ◽  
Author(s):  
Salvi Asefi-Najafabady ◽  
Sassan Saatchi
Keyword(s):  
West Africa ◽  
Tropical Forests ◽  
Large Scale ◽  
Forest Canopy ◽  
Central Africa ◽  
Extreme Rainfall ◽  
Research Unit ◽  
Congo Basin ◽  
West And Central Africa ◽  
Rainfall Anomalies

During the last decade, strong negative rainfall anomalies resulting from increased sea surface temperature in the tropical Atlantic have caused extensive droughts in rainforests of western Amazonia, exerting persistent effects on the forest canopy. In contrast, there have been no significant impacts on rainforests of West and Central Africa during the same period, despite large-scale droughts and rainfall anomalies during the same period. Using a combination of rainfall observations from meteorological stations from the Climate Research Unit (CRU; 1950–2009) and satellite observations of the Tropical Rainfall Measuring Mission (TRMM; 1998–2010), we show that West and Central Africa experienced strong negative water deficit (WD) anomalies over the last decade, particularly in 2005, 2006 and 2007. These anomalies were a continuation of an increasing drying trend in the region that started in the 1970s. We monitored the response of forests to extreme rainfall anomalies of the past decade by analysing the microwave scatterometer data from QuickSCAT (1999–2009) sensitive to variations in canopy water content and structure. Unlike in Amazonia, we found no significant impacts of extreme WD events on forests of Central Africa, suggesting potential adaptability of these forests to short-term severe droughts. Only forests near the savanna boundary in West Africa and in fragmented landscapes of the northern Congo Basin responded to extreme droughts with widespread canopy disturbance that lasted only during the period of WD. Time-series analyses of CRU and TRMM data show most regions in Central and West Africa experience seasonal or decadal extreme WDs (less than −600 mm). We hypothesize that the long-term historical extreme WDs with gradual drying trends in the 1970s have increased the adaptability of humid tropical forests in Africa to droughts.

scholarly journals State and evolution of the African rainforests between 1990 and 2010

2013 ◽  
Vol 368 (1625) ◽  
pp. 20120300 ◽  
Author(s):  
Philippe Mayaux ◽  
Jean-François Pekel ◽  
Baudouin Desclée ◽  
François Donnay ◽  
Andrea Lupi ◽  
...  
Keyword(s):  
West Africa ◽  
Forest Cover ◽  
Central Africa ◽  
Congo Basin ◽  
Landsat Images ◽  
Deforestation Rate ◽  
Rural And Urban ◽  
Moderate Resolution ◽  
Underlying Causes ◽  
Moderate Resolution Imaging Spectroradiometer

This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr −1 for the period 1990–2000 and 0.14% yr −1 for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are also identified as strong underlying causes of deforestation in this study.

scholarly journals Understanding the mechanism of land-cover related climate change in the low latitudes

MAUSAM ◽  
2021 ◽  
Vol 59 (3) ◽  
pp. 297-312
Author(s):  
HEIKO PAETH
Keyword(s):  
Land Cover ◽  
West Africa ◽  
Vegetation Cover ◽  
Land Surface ◽  
Large Scale ◽  
Rainfall Amount ◽  
Congo Basin ◽  
Convective Precipitation ◽  
Land Cover Changes ◽  
Low Latitudes

Rainfall variability in the low latitudes in general and over tropical and sub-tropical Africa in particular, is largely affected by land surface characteristics like, vegetation cover, albedo and soil moisture. Understanding the local and dynamical effects of land-cover changes is crucial to future climate prediction, given ongoing population growth and increasing agricultural needs in Africa. Here, a set of sensitivity studies with a synoptic-scale regional climate model is presented, prescribing idealized scenarios of reduced vegetation cover over Africa. Beside the vegetation ratio itself, the leaf area index, forest ratio, surface albedo and roughness length are changed as well, in order to obtain a consistent scenario of land surface degradation. In addition, a second set of experiments is realized with altered soil parameters as expected to be coming alongwith a reduction in vegetation cover.   Seasonal rainfall amount decreases substantially when the present-day vegetation continuously disappears. The strongest changes are found over the Congo Basin and subsaharan West Africa, where the summer monsoon precipitation diminishes by up to 2000 mm and 600 mm, respectively. The rainfall response to vegetation changes is non-linear and statistically significant over large parts of subsaharan Africa. Convective precipitation is more sensitive than large-scale precipitation.   The most prominent effect of land degradation is a decrease (increase) of latent (sensible) heat fluxes. As a consequence, the large-scale thermal gradients, as a key factor in the monsoonal flow over Africa, are modified leading to a southward shift of the intertropical convergence zone and enhanced moisture advection over the southernmost part of West Africa and the central Congo Basin. The mid-tropospheric jet and wave dynamics are barely affected by land-cover changes. Although the large-scale dynamical response is favourable to increasing rainfall amount, the moisture budget is predominantly governed by reduced evapotranspiration, overcompensating the positive dynamical effect and inducing a weakening of the regional-scale water recycling. The related changes in the soil properties may additionally contribute to a reduction in rainfall amount, albeit of lower amplitude.

scholarly journals Challenges in Estimating Tropical Forest Canopy Height from Planet Dove Imagery

2020 ◽  
Vol 12 (7) ◽  
pp. 1160 ◽  
Author(s):  
Ovidiu Csillik ◽  
Pramukta Kumar ◽  
Gregory P. Asner
Keyword(s):  
Tropical Forests ◽  
Spatial Resolution ◽  
Large Scale ◽  
Forest Canopy ◽  
Satellite Image ◽  
Spectral Projection ◽  
Forest Degradation ◽  
Canopy Height ◽  
Textural Features ◽  
Conservation Actions

Monitoring tropical forests using spaceborne and airborne remote sensing capabilities is important for informing environmental policies and conservation actions. Developing large-scale machine learning estimation models of forest structure is instrumental in bridging the gap between retrospective analysis and near-real-time monitoring. However, most approaches use moderate spatial resolution satellite data with limited capabilities of frequent updating. Here, we take advantage of the high spatial and temporal resolutions of Planet Dove images and aim to automatically estimate top-of-canopy height (TCH) for the biologically diverse country of Peru from satellite imagery at 1 ha spatial resolution by building a model that associates Planet Dove textural features with airborne light detection and ranging (LiDAR) measurements of TCH. We use and modify features derived from Fourier textural ordination (FOTO) of Planet Dove images using spectral projection and train a gradient boosted regression for TCH estimation. We discuss the technical and scientific challenges involved in the generation of reliable mechanisms for estimating TCH from Planet Dove satellite image spectral and textural features. Our developed software toolchain is a robust and generalizable regression model that provides a root mean square error (RMSE) of 4.36 m for Peru. This represents a helpful advancement towards better monitoring of tropical forests and improves efforts in reducing emissions from deforestation and forest degradation (REDD+), an important climate change mitigation approach.

scholarly journals Promising High-Yielding Tetraploid Plantain-Bred Hybrids in West Africa

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Abdou Tenkouano ◽  
Niéyidouba Lamien ◽  
Josephine Agogbua ◽  
Delphine Amah ◽  
Rony Swennen ◽  
...  
Keyword(s):  
West Africa ◽  
Research And Development ◽  
Cote D'ivoire ◽  
Côte D’Ivoire ◽  
Central Africa ◽  
International Institute ◽  
The West ◽  
Cote D’Ivoire ◽  
Côte D'ivoire ◽  
West And Central Africa

The devastating threat of black leaf streak disease caused by Pseudocercospora fijiensis on plantain production in West Africa spurred the development of resistant hybrids. The goal of this research and development (R&D) undertaken was assessing the development and dissemination of two plantain hybrids PITA 3 and FHIA 21 bred in the 1980s by the International Institute of Tropical Agriculture (IITA, Nigeria) and the Fundación Hondureña de Investigación Agrícola (FHIA, Honduras), respectively. In Côte d’Ivoire, plantain growers selected PITA 3 and FHIA 21 based on their improved agronomic characteristics and, between 2012 and 2016, they were massively propagated and distributed to farmers in Benin, Burkina Faso, Côte d’Ivoire, and Togo under the West Africa Agricultural Productivity Program (WAAAP) coordinated by the West and Central Africa Council for Agricultural Research and Development (CORAF). In 2016, the Centre National de Recherche Agronomique in Côte d’Ivoire included the hybrids in the improved cultivar directory. This R&D activity illustrates how three decades of crossbreeding, selection, and distribution led to local acceptance. It also highlights how a CORAF-led partnership harnessed CGIAR research for development. The dissemination and acceptance of these plantain hybrids will enhance the sustainable intensification in plantain-based farming systems across the humid lowlands of West and Central Africa.

scholarly journals Community Policing and the Engagement of Pastoral Terrorism in West Africa

SAGE Open ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 215824401989370
Author(s):  
Kingsley U. Ejiogu
Keyword(s):  
West Africa ◽  
Community Policing ◽  
Central Africa ◽  
Social Engineering ◽  
Indigenous Communities ◽  
Mass Murder ◽  
Intelligence Community ◽  
Global Consciousness ◽  
West And Central Africa ◽  
Social Policing

Within a changing global consciousness for international guardianship of the targets of terrorism, this article explores the broad narratives, strengths, and limitations of adopting community policing for the control of herdsmen terrorism in West Africa. It follows the search by social engineering and criminal justice practitioners for a relational and experiential agent for social change against destructive terrorist tendencies and its eroding influence on the sensibilities of human civilization. The article frames an approach for creating a social policing environment in rural and poor communities along pastoral transhumance routes in West and Central Africa. The mass murder of indigenous communities by the migratory and transborder terror groups in this region is a crime against humanity. The adoption of the concept of “connected communities” is suggested to create a multilayered and all-involving intelligence community policing shield in individual communities under siege of the pastoralists.

scholarly journals Assessing Freshwater Changes over Southern and Central Africa (2002–2017)

2021 ◽  
Vol 13 (13) ◽  
pp. 2543
Author(s):  
Ikechukwu Kalu ◽  
Christopher E. Ndehedehe ◽  
Onuwa Okwuashi ◽  
Aniekan E. Eyoh
Keyword(s):  
Large Scale ◽  
Central Africa ◽  
Principal Component ◽  
River Basins ◽  
Congo Basin ◽  
Study Region ◽  
South Central ◽  
Terrestrial Water ◽  
Relationship Of ◽  
The Relationship

In large freshwater river basins across the globe, the composite influences of large-scale climatic processes and human activities (e.g., deforestation) on hydrological processes have been studied. However, the knowledge of these processes in this era of the Anthropocene in the understudied hydrologically pristine South Central African (SCA) region is limited. This study employs satellite observations of evapotranspiration (ET), precipitation and freshwater between 2002 and 2017 to explore the hydrological patterns of this region, which play a crucial role in global climatology. Multivariate methods, including the rotated principal component analysis (rPCA) were used to assess the relationship of terrestrial water storage (TWS) in response to climatic units (precipitation and ET). The use of the rPCA technique in assessing changes in TWS is warranted to provide more information on hydrological changes that are usually obscured by other dominant naturally-driven fluxes. Results show a low trend in vegetation transpiration due to deforestation around the Congo basin. Overall, the Congo (r2 = 76%) and Orange (r2 = 72%) River basins maintained an above-average consistency between precipitation and TWS throughout the study region and period. Consistent loss in freshwater is observed in the Zambezi (−9.9 ± 2.6 mm/year) and Okavango (−9.1 ± 2.5 mm/year) basins from 2002 to 2008. The Limpopo River basin is observed to have a 6% below average reduction in rainfall rates which contributed to its consistent loss in freshwater (−4.6 ± 3.2 mm/year) from 2006 to 2012.Using multi-linear regression and correlation analysis we show that ET contributes to the variability and distribution of TWS in the region. The relationship of ET with TWS (r = 0.5) and rainfall (r = 0.8) over SCA provides insight into the role of ET in regulating fluxes and the mechanisms that drive precipitation in the region. The moderate ET–TWS relationship also shows the effect of climate and anthropogenic influence in their interactions.

scholarly journals Notes on the genus Abantis Hopffer, 1855 with description of two new species (Lepidoptera: Hesperiidae, Pyrginae)

2016 ◽  
Vol 48 (1) ◽  
pp. 53
Author(s):  
Claudio Belcastro ◽  
Philippe Oremans
Keyword(s):  
New Species ◽  
West Africa ◽  
Forest Canopy ◽  
Central Africa ◽  
Conclusive Evidence ◽  
Species Level ◽  
Two New Species ◽  
Flower Visiting ◽  
Almost All

The Afrotropical genus <em>Abantis</em> Hopffer, 1855 includes about 23 species so far, all quite rare. In Evans’ Catalogue of the African Hesperiidae only 14 species were listed but, apart from a few newly discovered ones, some of the subspecies indicated over there have subsequently been raised to species level, although they look very similar in facies with previously recognised taxa. This article shows the presence of an unrecognised species similar to <em>A. lucretia</em> Druce, 1909 in West Africa, namely <em>A. fabiana</em> sp. n., and another one similar to both<em> A. contigua</em> Evans, 1937 and<em> A. elegantula</em> Mabille, 1890 in Central Africa, namely <em>A. torbeni</em> sp. n. The rarity in collections of almost all forest-dwelling <em>Abantis</em> spp. is reported as connected to their habit of flying high in the forest canopy, but the authors have no conclusive evidence of it. Most <em>Abantis</em> are hill-toppers, mud lovers and are attracted by dead animals (fish and turtles), although some of them are also flower-visiting.

Soils of the lowland forests of West and Central Africa

1996 ◽  
Vol 104 ◽  
pp. 15-29 ◽  
Author(s):  
A. S. R. Juo ◽  
L. P. Wilding
Keyword(s):  
East Africa ◽  
Central Africa ◽  
Congo Basin ◽  
The West ◽  
Forest Zone ◽  
Lower Elevation ◽  
Lowland Forests ◽  
West And Central Africa ◽  
Hydrological Cycles ◽  
Great Rift Valley

The forest zone of West and Central Africa comprises the coastal and adjacent inland regions bounded the semi-deciduous forests in the west and the equatorial forests in central Africa and the Congo basin. Sedimentary plains, developed mostly on weathered sandy materials, lie along the coastal stretches and cover vast areas of the Congo basin. Behind the coast the plain rises gradually to hills and plateaus of much lower elevation than those of the highlands of East Africa. Two great rivers, the Niger and the Congo, which discharge huge volumes of fresh water to the Atlantic Ocean, are major contributors to the hydrological cycles of the rain forests ecosystems of the Guinea–Congo Region. The Niger originates from the forested highlands of Guinea and discharges its waters into the Bight of Benin by way of a large delta in southern Nigeria. The Congo basin occupies an immense area of 750 000 km2, surrounded by Pre-Cambrian uplands. The alluvial floor of the saucer-shaped basin is flat, and marshes and swamps comprise a large proportion of the total area. The highlands and plateaus along the rim are low to the west and north and higher to the south. To the east, they merge with the mountains of the Great Rift Valley of East Africa (Gann & Duignan 1972; Hance 1975; Grove 1978; Hamilton 1989).

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