Prolonged and frequent droughts in Southern California present hazards and uncertainty for the re... more Prolonged and frequent droughts in Southern California present hazards and uncertainty for the region's increasing population, resulting in proactive and aggressive water management strategies. The goal of this study is to present a case study of the San Diego region's rainfall and temperature time series analysis in order to determine annual and seasonal trends and their significance. Rainfall and temperature data from 20 rain-gauged stations were analyzed for the period 1985-2017. A project database was set up for data compilation and quality control, and a Mann-Kendall test for trend analysis was used. Results indicated that rainfall in the region decreased both annually and during the rainy season (November-April) by up to 0.14 mm between 1985 and 2017, although not in a statistically significant manner, except at two rainfall observation stations. Rainfall appears to have increased in many of the stations examined during the dry season (May-October), with an average magnitude of 0.09 mm. Analysis of daily minimum and maximum temperature reveals overall average annual and seasonal increases of 0.07 • C and 0.04 • C, respectively, with statistically significant increases at 10 of 17 for minimum temperature, and 0.27 • C and −0.25 • C with statistically significant increases at 9 of 16 for maximum temperature. Temperature tends to have increased more during the dry season compared to the rainy season. This study reveals an overall decreasing tendency in rainfall and an increasing tendency in minimum and maximum temperatures (although not statistically significant) in the San Diego region between 1985 and 2017, which likely contributed to important management implications for the region's water resources.
The U.S. State of California has experienced frequent drought events, hotter temperatures and oth... more The U.S. State of California has experienced frequent drought events, hotter temperatures and other disruptions to the climate system whose effects on ecosystems have been widely reported in recent decades. Studies primarily confined to specific vegetation communities or species, individual drought incidents, or analysis over a relatively short intervals, has limited our understanding of the broad-scale effects on tree cover and the spatiotemporal variability of effects across broader regions. We focused analysis on multi-annual land cover and land surface change to assess patterns and trends in tree cover loss in tree-dominated Californian ecoregions from 1986 to 2019. The top three years of total tree cover loss for the state were 2018 (1901 km2), 2015 (1556 km2), and 2008 (1549 km2). Overall, annual tree cover loss had upward trends. Tree cover loss rapidly surged later in the study period and was apparently driven by climate stress and wildfires. Underlying geographic variabilit...
ABSTRACT Sustainably managed forests have multiple environmental and socio-economic functions whi... more ABSTRACT Sustainably managed forests have multiple environmental and socio-economic functions which are important at the global, national and local scales, and they play a vital part in sustainable development. Reliable and up-to-date information on the state of forest resources -not only on area and area change, but also on such variables as growing stock, wood and non-wood products, carbon, protected areas, use of forests for recreation and other services, biological diversity and forests' contribution to national economies -is crucial to support decision-making for policies and programmes in forestry and sustainable development at all levels. Under the umbrella of the Global Forest Resources Assessment 2010 (FRA 2010) and together with members of the Collaborative Partnership on Forests (CPF) and other partners, FAO has initiated a special study to identify the elements of forest degradation and the best practices for assessing them. The objectives of the initiative are to help strengthen the capacity of countries to assess, monitor and report on forest degradation by: Identifying specific elements and indicators of forest degradation and degraded forests; Classifying elements and harmonizing definitions; Identifying and describing existing and promising assessment methodologies; Developing assessment tools and guidelines Expected outcomes and benefits of the initiative include: Better understanding of the concept and components of forest degradation; An analysis of definitions of forest degradation and associated terms; Guidelines and effective, cost-efficient tools and techniques to help assess and monitor forest degradation; and Enhanced ability to meet current and future reporting requirements on forest degradation.
California has, in recent years, become a hotspot of interannual climatic variability, recording ... more California has, in recent years, become a hotspot of interannual climatic variability, recording devastating climate-related disturbances with severe effects on tree resources. Understanding the patterns of tree cover change associated with these events is vital for developing strategies to sustain critical habitats of endemic and threatened vegetation communities. We assessed patterns of tree cover change, especially the effects of the 2012–2016 drought within the distribution range of blue oak (Quercus douglasii), an endemic tree species to California with a narrow geographic extent. We utilized multiple, annual land-cover and land-surface change products from the U.S. Geological Survey (USGS) Land Change Monitoring, Assessment and Projection (LCMAP) project along with climate and wildfire datasets to monitor changes in tree cover state and condition and examine their relationships with interannual climate variability between 1985 and 2016. Here, we refer to a change in tree cover...
Prolonged and frequent droughts in Southern California present hazards and uncertainty for the re... more Prolonged and frequent droughts in Southern California present hazards and uncertainty for the region’s increasing population, resulting in proactive and aggressive water management strategies. The goal of this study is to present a case study of the San Diego region’s rainfall and temperature time series analysis in order to determine annual and seasonal trends and their significance. Rainfall and temperature data from 20 rain-gauged stations were analyzed for the period 1985–2017. A project database was set up for data compilation and quality control, and a Mann-Kendall test for trend analysis was used. Results indicated that rainfall in the region decreased both annually and during the rainy season (November–April) by up to 0.14 mm between 1985 and 2017, although not in a statistically significant manner, except at two rainfall observation stations. Rainfall appears to have increased in many of the stations examined during the dry season (May–October), with an average magnitude o...
The IUFRO Occasional Paper Series was initiated in 1994 and is intended for rapid dissemination o... more The IUFRO Occasional Paper Series was initiated in 1994 and is intended for rapid dissemination of publications reflecting IUFRO activities, reports of meetings, frameworks for Task Forces, and collaboration with other organizations. This in-house publication series has been converted into an electronic series in early 2005, underlining its ambition of bringing forward IUFRO's immediate position on important forest-related issues. Publications in this series are available on our website www.iufro.org under Publications or directly at . Occasional Paper No. 1 -Global Change and Terrestrial Ecosystems (GCTE) -Effects of Global Change on Managed Forests Occasional Paper No. 2 -Actas de la Reunión Internacional sobre La Red de Información Forestal para América Latina y el Caribe (out of print!) Occasional Paper No. 3 -Planning a Conference Occasional Paper No. 4 -IUFRO Task Force "Forest, Climate Change and Air Pollution" -impacts of climate change on forests and forest-dependent people and put strategies in place to adapt to them. 3) Improving the adaptive capacity of forest-dependent communities is important in order to reduce their vulnerability to the effects of climate change. Participatory approaches should be used to obtain a better understanding of local knowledge and perceptions of climatic change and to raise awareness about vulnerabilities and related adaptation measures. Moreover, there is a need to develop and reorient educational systems and programmes. 4) Climate change is adding to a range of other pressures -such as agricultural expansion and the over-use of forests -on forest ecosystems in Africa, some of which are currently more pressing than climate change. Measures that reduce non-climatic pressures can help reduce the overall vulnerability of forest ecosystems. Such measures, including forest restoration and rehabilitation, can be implemented in an integrated manner as part of sustainable forest management. 5) The development and implementation of adaptation measures as part of sustainable forest management need to be underpinned by new modes of governance that are sensitive to context, take a broad view of community needs, and respond quickly to policy learning. Governance that enables effective stakeholder and community participation, transparent and accountable decision-making, secure land ownership and tenure, and the equitable sharing of benefits and responsibilities needs to be promoted. 6) Climate-change adaptation planning in Africa is hampered by a lack of information about current and future climate-related impacts and vulnerabilities. Reliable projections of regional and local impacts require investments in research and monitoring infrastructure and increased support for early-warning systems and preparedness measures. 7) Forests can play an important role in achieving broader climate-change adaptation goals but may be threatened by impacts from other sectors. Strategies for adapting forests to climate change should be coordinated with those of other sectors and integrated into national and regional development programmes and strategies.
The Upper Guinean Forest region of West Africa, a globally significant biodiversity hotspot, is a... more The Upper Guinean Forest region of West Africa, a globally significant biodiversity hotspot, is among the driest and most human-impacted tropical ecosystems. We used Landsat to study forest degradation, loss, and recovery in the forest reserves of Ghana from 2003 to 2019. Annual canopy cover maps were generated using random forests and results were temporally segmented using the LandTrendr algorithm. Canopy cover was predicted with a predicted-observed r<sup>2</sup> of 0.76, mean absolute error of 12.8%, and mean error of 1.3%. Forest degradation, loss, and recovery were identified as transitions between closed (&gt;60% cover), open (15–60% cover) and low tree cover (&lt; 15% cover) classes. Change was relatively slow from 2003 to 2015, but there was more disturbance than recovery resulting in a gradual decline in closed canopy forests. In 2016, widespread fires associated with El Niño drought caused forest loss and degradation across more than 12% of the moist semi-deciduous and upland evergreen forest types. The workflow was implemented in Google Earth Engine, allowing stakeholders to visualize the results and download summaries. Information about historical disturbances will help to prioritize locations for future studies and target forest protection and restoration activities aimed at increasing resilience.
The Upper Guinean region of West Africa exhibits strong geographic variation in land use, climate... more The Upper Guinean region of West Africa exhibits strong geographic variation in land use, climate, vegetation, and human population and has experienced phenomenal biophysical and socioeconomic changes in recent decades. All of these factors influence spatial heterogeneity and temporal trends in fires, but their combined effects on fire regimes are not well understood. The main objectives of this study were to characterize the spatial patterns and interrelationships of multiple fire regime components, identify recent trends in fire activity, and explore the relative influences of climate, topography, vegetation type, and human activity on fire regimes. Fire regime components, including active fire density, burned area, fire season length, and fire radiative power, were characterized using MODIS fire products from 2003 to 2015. Both active fire and burned area were most strongly associated with vegetation type, whereas fire season length was most strongly influenced by climate and topography variables, and fire radiative power was most strongly influenced by climate. These associations resulted in a gradient of increasing fire activity from forested coastal regions to the savanna-dominated interior, as well as large variations in burned area and fire season length within the savanna regions and high fire radiative power in the westernmost coastal regions. There were increasing trends in active fire detections in parts of the Western Guinean Lowland Forests ecoregion and decreasing trends in both active fire detections and burned area in savanna-dominated ecoregions. These results portend that ongoing regional landscape and socioeconomic changes along with climate change will lead to further changes in the fire regimes in West Africa. Efforts to project future fire regimes and develop regional strategies for adaptation will need to encompass multiple components of the fire regime and consider multiple drivers, including land use as well as climate.
Prolonged and frequent droughts in Southern California present hazards and uncertainty for the re... more Prolonged and frequent droughts in Southern California present hazards and uncertainty for the region's increasing population, resulting in proactive and aggressive water management strategies. The goal of this study is to present a case study of the San Diego region's rainfall and temperature time series analysis in order to determine annual and seasonal trends and their significance. Rainfall and temperature data from 20 rain-gauged stations were analyzed for the period 1985-2017. A project database was set up for data compilation and quality control, and a Mann-Kendall test for trend analysis was used. Results indicated that rainfall in the region decreased both annually and during the rainy season (November-April) by up to 0.14 mm between 1985 and 2017, although not in a statistically significant manner, except at two rainfall observation stations. Rainfall appears to have increased in many of the stations examined during the dry season (May-October), with an average magnitude of 0.09 mm. Analysis of daily minimum and maximum temperature reveals overall average annual and seasonal increases of 0.07 • C and 0.04 • C, respectively, with statistically significant increases at 10 of 17 for minimum temperature, and 0.27 • C and −0.25 • C with statistically significant increases at 9 of 16 for maximum temperature. Temperature tends to have increased more during the dry season compared to the rainy season. This study reveals an overall decreasing tendency in rainfall and an increasing tendency in minimum and maximum temperatures (although not statistically significant) in the San Diego region between 1985 and 2017, which likely contributed to important management implications for the region's water resources.
The U.S. State of California has experienced frequent drought events, hotter temperatures and oth... more The U.S. State of California has experienced frequent drought events, hotter temperatures and other disruptions to the climate system whose effects on ecosystems have been widely reported in recent decades. Studies primarily confined to specific vegetation communities or species, individual drought incidents, or analysis over a relatively short intervals, has limited our understanding of the broad-scale effects on tree cover and the spatiotemporal variability of effects across broader regions. We focused analysis on multi-annual land cover and land surface change to assess patterns and trends in tree cover loss in tree-dominated Californian ecoregions from 1986 to 2019. The top three years of total tree cover loss for the state were 2018 (1901 km2), 2015 (1556 km2), and 2008 (1549 km2). Overall, annual tree cover loss had upward trends. Tree cover loss rapidly surged later in the study period and was apparently driven by climate stress and wildfires. Underlying geographic variabilit...
ABSTRACT Sustainably managed forests have multiple environmental and socio-economic functions whi... more ABSTRACT Sustainably managed forests have multiple environmental and socio-economic functions which are important at the global, national and local scales, and they play a vital part in sustainable development. Reliable and up-to-date information on the state of forest resources -not only on area and area change, but also on such variables as growing stock, wood and non-wood products, carbon, protected areas, use of forests for recreation and other services, biological diversity and forests&amp;amp;amp;amp;#39; contribution to national economies -is crucial to support decision-making for policies and programmes in forestry and sustainable development at all levels. Under the umbrella of the Global Forest Resources Assessment 2010 (FRA 2010) and together with members of the Collaborative Partnership on Forests (CPF) and other partners, FAO has initiated a special study to identify the elements of forest degradation and the best practices for assessing them. The objectives of the initiative are to help strengthen the capacity of countries to assess, monitor and report on forest degradation by: Identifying specific elements and indicators of forest degradation and degraded forests; Classifying elements and harmonizing definitions; Identifying and describing existing and promising assessment methodologies; Developing assessment tools and guidelines Expected outcomes and benefits of the initiative include: Better understanding of the concept and components of forest degradation; An analysis of definitions of forest degradation and associated terms; Guidelines and effective, cost-efficient tools and techniques to help assess and monitor forest degradation; and Enhanced ability to meet current and future reporting requirements on forest degradation.
California has, in recent years, become a hotspot of interannual climatic variability, recording ... more California has, in recent years, become a hotspot of interannual climatic variability, recording devastating climate-related disturbances with severe effects on tree resources. Understanding the patterns of tree cover change associated with these events is vital for developing strategies to sustain critical habitats of endemic and threatened vegetation communities. We assessed patterns of tree cover change, especially the effects of the 2012–2016 drought within the distribution range of blue oak (Quercus douglasii), an endemic tree species to California with a narrow geographic extent. We utilized multiple, annual land-cover and land-surface change products from the U.S. Geological Survey (USGS) Land Change Monitoring, Assessment and Projection (LCMAP) project along with climate and wildfire datasets to monitor changes in tree cover state and condition and examine their relationships with interannual climate variability between 1985 and 2016. Here, we refer to a change in tree cover...
Prolonged and frequent droughts in Southern California present hazards and uncertainty for the re... more Prolonged and frequent droughts in Southern California present hazards and uncertainty for the region’s increasing population, resulting in proactive and aggressive water management strategies. The goal of this study is to present a case study of the San Diego region’s rainfall and temperature time series analysis in order to determine annual and seasonal trends and their significance. Rainfall and temperature data from 20 rain-gauged stations were analyzed for the period 1985–2017. A project database was set up for data compilation and quality control, and a Mann-Kendall test for trend analysis was used. Results indicated that rainfall in the region decreased both annually and during the rainy season (November–April) by up to 0.14 mm between 1985 and 2017, although not in a statistically significant manner, except at two rainfall observation stations. Rainfall appears to have increased in many of the stations examined during the dry season (May–October), with an average magnitude o...
The IUFRO Occasional Paper Series was initiated in 1994 and is intended for rapid dissemination o... more The IUFRO Occasional Paper Series was initiated in 1994 and is intended for rapid dissemination of publications reflecting IUFRO activities, reports of meetings, frameworks for Task Forces, and collaboration with other organizations. This in-house publication series has been converted into an electronic series in early 2005, underlining its ambition of bringing forward IUFRO's immediate position on important forest-related issues. Publications in this series are available on our website www.iufro.org under Publications or directly at . Occasional Paper No. 1 -Global Change and Terrestrial Ecosystems (GCTE) -Effects of Global Change on Managed Forests Occasional Paper No. 2 -Actas de la Reunión Internacional sobre La Red de Información Forestal para América Latina y el Caribe (out of print!) Occasional Paper No. 3 -Planning a Conference Occasional Paper No. 4 -IUFRO Task Force "Forest, Climate Change and Air Pollution" -impacts of climate change on forests and forest-dependent people and put strategies in place to adapt to them. 3) Improving the adaptive capacity of forest-dependent communities is important in order to reduce their vulnerability to the effects of climate change. Participatory approaches should be used to obtain a better understanding of local knowledge and perceptions of climatic change and to raise awareness about vulnerabilities and related adaptation measures. Moreover, there is a need to develop and reorient educational systems and programmes. 4) Climate change is adding to a range of other pressures -such as agricultural expansion and the over-use of forests -on forest ecosystems in Africa, some of which are currently more pressing than climate change. Measures that reduce non-climatic pressures can help reduce the overall vulnerability of forest ecosystems. Such measures, including forest restoration and rehabilitation, can be implemented in an integrated manner as part of sustainable forest management. 5) The development and implementation of adaptation measures as part of sustainable forest management need to be underpinned by new modes of governance that are sensitive to context, take a broad view of community needs, and respond quickly to policy learning. Governance that enables effective stakeholder and community participation, transparent and accountable decision-making, secure land ownership and tenure, and the equitable sharing of benefits and responsibilities needs to be promoted. 6) Climate-change adaptation planning in Africa is hampered by a lack of information about current and future climate-related impacts and vulnerabilities. Reliable projections of regional and local impacts require investments in research and monitoring infrastructure and increased support for early-warning systems and preparedness measures. 7) Forests can play an important role in achieving broader climate-change adaptation goals but may be threatened by impacts from other sectors. Strategies for adapting forests to climate change should be coordinated with those of other sectors and integrated into national and regional development programmes and strategies.
The Upper Guinean Forest region of West Africa, a globally significant biodiversity hotspot, is a... more The Upper Guinean Forest region of West Africa, a globally significant biodiversity hotspot, is among the driest and most human-impacted tropical ecosystems. We used Landsat to study forest degradation, loss, and recovery in the forest reserves of Ghana from 2003 to 2019. Annual canopy cover maps were generated using random forests and results were temporally segmented using the LandTrendr algorithm. Canopy cover was predicted with a predicted-observed r<sup>2</sup> of 0.76, mean absolute error of 12.8%, and mean error of 1.3%. Forest degradation, loss, and recovery were identified as transitions between closed (&gt;60% cover), open (15–60% cover) and low tree cover (&lt; 15% cover) classes. Change was relatively slow from 2003 to 2015, but there was more disturbance than recovery resulting in a gradual decline in closed canopy forests. In 2016, widespread fires associated with El Niño drought caused forest loss and degradation across more than 12% of the moist semi-deciduous and upland evergreen forest types. The workflow was implemented in Google Earth Engine, allowing stakeholders to visualize the results and download summaries. Information about historical disturbances will help to prioritize locations for future studies and target forest protection and restoration activities aimed at increasing resilience.
The Upper Guinean region of West Africa exhibits strong geographic variation in land use, climate... more The Upper Guinean region of West Africa exhibits strong geographic variation in land use, climate, vegetation, and human population and has experienced phenomenal biophysical and socioeconomic changes in recent decades. All of these factors influence spatial heterogeneity and temporal trends in fires, but their combined effects on fire regimes are not well understood. The main objectives of this study were to characterize the spatial patterns and interrelationships of multiple fire regime components, identify recent trends in fire activity, and explore the relative influences of climate, topography, vegetation type, and human activity on fire regimes. Fire regime components, including active fire density, burned area, fire season length, and fire radiative power, were characterized using MODIS fire products from 2003 to 2015. Both active fire and burned area were most strongly associated with vegetation type, whereas fire season length was most strongly influenced by climate and topography variables, and fire radiative power was most strongly influenced by climate. These associations resulted in a gradient of increasing fire activity from forested coastal regions to the savanna-dominated interior, as well as large variations in burned area and fire season length within the savanna regions and high fire radiative power in the westernmost coastal regions. There were increasing trends in active fire detections in parts of the Western Guinean Lowland Forests ecoregion and decreasing trends in both active fire detections and burned area in savanna-dominated ecoregions. These results portend that ongoing regional landscape and socioeconomic changes along with climate change will lead to further changes in the fire regimes in West Africa. Efforts to project future fire regimes and develop regional strategies for adaptation will need to encompass multiple components of the fire regime and consider multiple drivers, including land use as well as climate.
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Papers by Francis Dwomoh