Spatio-temporal analyses of impacts of multiple climatic hazards in a savannah ecosystem of Ghana

Ghana’s savannah ecosystem has been subjected to a number of climatic hazards of varying severity. This paper presents a spatial, time-series analysis of the impacts of multiple hazards on the ecosystem and human livelihoods over the period 1983-2012, using the Upper East Region of Ghana as a case study. Our aim is to understand the nature of hazards (their frequency, magnitude and duration) and how they cumulatively affect humans. Primary data were collected using questionnaires, focus group discussions, in-depth interviews and personal observations. Secondary data were collected from documents and reports. Calculations of the standard precipitation index (SPI) and crop failure index used rainfall data from 4 weather stations (Manga, Binduri, Vea and Navrongo) and crop yield data of 5 major crops (maize, sorghum, millet, rice and groundnuts) respectively. Temperature and windstorms were analysed from the observed weather data. We found that temperatures were consistently high and increasing. From the SPI, drought frequency varied spatially from 9 at Binduri to 13 occurrences at Vea; dry spells occurred at least twice every year and floods occurred about 6 times on average, with slight spatial variations, during 1988-2012, a period with consistent data from all stations. Impacts from each hazard varied spatio-temporally. Within the study period, more 70% of years recorded severe crop losses with greater impacts when droughts and floods occur in the same year, especially in low lying areas. The effects of crop losses were higher in districts with no/little irrigation (Talensi, Nabdam, Garu-Tempane, Kassena-Nankana East). Frequency and severity of diseases and sicknesses such as cerebrospinal meningitis, heat rashes, headaches and malaria related to both dry and wet conditions have increased steadily over time. Other impacts recorded with spatio-temporal variations included destruction to housing, displacement, injury and death of people. These impacts also interacted. For example, sicknesses affected labour output; crop losses were blamed for high malnutrition; and reconstruction of properties demanded financial resources largely from sale of agricultural produce. These frequent impacts and their interactions greatly explain the persistent poverty in the area

Regeneration patterns, environmental filtering and tree species coexistence in a temperate forest

• Forest ecologists researching the functional basis of tree regeneration patterns and species coexistence often attempt to correlate traits with light-gradient partitioning. However, an exclusive focus on light can overlook other important drivers of forest dynamics. • We measured light, temperatures, humidity and sapling densities in each of four phases of a forest dynamic mosaic in New Zealand: shaded understoreys, tree-fall gaps, treefern groves and clearings. We then measured leaf, wood and seed traits, as potential predictors of species’ regeneration patterns. • Saplings of 18 out of 21 species were significantly associated with one or other of the four phases, and associations were best predicted by a two-trait model (leaf size, wood density) explaining 51% of observed variation. Species associated with treefall gaps had traits favouring light pre-emption (large leaves, low-density wood), whereas those establishing in clearings mostly had small leaves and dense wood, traits probably conferring resistance to the frosts and summer water deficits that saplings were exposed to there. • The dynamics of some forests cannot be explained adequately by light-gradient partitioning through a growth vs shade tolerance tradeoff, underpinned by the leaf economics spectrum. Consideration of multiple environmental filters and multiple traits will enhance understanding of regeneration patterns and species coexistence

Stream turbidity responses to storm events in a pristine rainforest watershed on the Coral Coast of southern Fiji

© 2016 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research On the Coral Coast of Viti Levu Island in Fiji, inadequate knowledge of suspended sediment delivery patterns in small pristine coastal watersheds hinders any future assessment of accelerated erosion in disturbed areas nearby. This study adopts a rainfall–stream turbidity monitoring approach in the Votua Creek, which drains a small, steep but minimally-disturbed coastal rainforest catchment. Storm rainfall characteristics, stream depth and water turbidity were continuously monitored over one complete Fiji wet season from October 2009 to April 2010. The aim was to evaluate whether these parameters provide sufficient information to illustrate basic features of storm–sediment transport responses, in the case of limited stream gauging and very simple sediment rating curves. This is important because Pacific Island nations like Fiji do not have the resources to initiate long-term gauging and sediment sampling programmes across numerous small catchments. A significant power function demonstrates that turbidity (T) is a suitable proxy for total suspended solids (TSS) for turbidity measurements above 5 NTU, with TSS=0.930T1.111 (r=0.98, P\u3c0.001). Over the study period, 10 individual storms 11.2–120.1 mm in size produced a ‘significant turbidity response’ (STR) in the Votua Creek. Rainfall parameters (totals and intensities) showed positive linear relationships (r=0.72–0.94) with stream turbidity parameters (mean, maximum, duration), whilst relationships of similar strength (r=0.76–0.98) were also derived between stream flow depth and turbidity. This implies that for small rainforest watersheds in Fiji, rainfall parameters offer no substantial disadvantage over flow as predictors of stream sediment responses to major storms. Event-based analysis revealed that negative (anticlockwise) hysteresis is a typical flow–turbidity pattern for STR events. Negative hysteresis is produced when secondary episodes of renewed (heavy) rainfall occur after maximum intensity, in the later phase of storm events. Tropical Cyclone Mick in December 2009 generated the largest flood and the greatest turbidity response (Tmax=1021 NTU, Tmean=207 NTU). This concurs with earlier work confirming that tropical cyclones are the most important events for sediment transport in Fiji stream networks

Regional and local emissions in red river delta, Northern Vietnam

Fine (PM2.2) and coarse (PM2.2–10) particles concurrently collected in urban (Hanoi) and rural (Lucnam) areas were analyzed for ionic and elemental compositions to provide input for PMF receptor modeling of emission sources in the Red River Delta (RRD), a key economic development region in Vietnam. Long-range transport (LRT) aerosol, coal fly ash from major coal-fired plants in RRD, and marine aerosols are regional sources, which explain the minor variability of the mass concentrations of fine particles across the region. Local sources include soil/resuspended road dust, local coal fly ash, and biomass burning. Soil/resuspended road dust is the largest source component of coarse particles at the two sites. It is more abundant in Hanoi than in Lucnam reflecting the urban–rural contrast in traffic and construction works. Receptor models reveal the incorporation of secondary sulfate, nitrate, and ammonium into the various primary particles, i.e., soot, minerals, soil organic matter, and sea salt. Soot particles from LRT carry the largest amounts of sulfate and ammonium mass concentrations measured at the two sites. Based on receptor models, the yields and possible chemical forms of secondary sulfate, nitrate, and ammonium in different types of primary particles can be inferred

The impact of climate change and urban growth on urban climate and heat stress in a subtropical city

Urban residents face increasing risk of heat stress due to the combined impact of climate change and intensification of the urban heat island (UHI) associated with urban growth. Considering the combined effect of urban growth and climate change is vital to understanding how temperatures in urban areas will change in the future. This study investigated the impact of urban growth and climate change on the UHI and heat stress in a subtropical city (Brisbane, Australia) in the present day (1991–2000) and medium term (2041–2050; RCP8.5) during summer. A control and urban growth scenario was used to compare the temperature increase from climate change alone with the temperature increase from climate change and urban growth. Average and minimum temperatures increased more with climate change and urban growth combined than with climate change alone, indicating that if urban growth is ignored, future urban temperatures could be underestimated. Under climate change alone, rural temperatures increased more than urban temperatures, decreasing the effect of the UHI by 0.4 °C at night and increasing the urban cool island by 0.8 °C during the day. With climate change, the number of hot days and nights doubled in urban and rural areas in 2041–2050 as compared to 1991–2000. The number of hot nights was higher in urban areas and with urban growth. Dangerous heat stress, defined as apparent temperature above 40 °C, increased with climate change and occurred on average 1–2 days every summer during 2041–2050, even in shaded conditions. There was higher temperature increases with urban growth and climate change than with climate change alone, indicating that reducing the effect of the UHI is vital to ensuring urban growth does not increase the heat stress risks that urban residents will face in the future

Spatio-temporal land use/cover dynamics and its implication for sustainable land use in Wanka watershed, northwestern highlands of Ethiopia

Long-term land use and land cover (LULC) dynamics information is essential to understand the trends and make necessary land management interventions, such as in the highlands of Ethiopia. This study analyzed six decades of LULC dynamics of Wanka watershed, Northwestern Ethiopian highlands. Two sets of aerial photographs (1957 and 2017), SPOT 5 and sentinel satellite imageries were analyzed. In addition, key informant interviews, focus group discussions and field observations were used to identify the drivers and impact of LULC change. It was found that cultivated and rural settlement land (CRSL), bare land, and urban built up area have been continuously expanded at the expenses of mainly forest and shrub lands. Over the entire study period (1957–2017) while the bare land and CRSL have increased by about 59% and 20% respectively, forest and shrub lands have declined by 59% and 57% respectively. Urban built up area has also expanded. The impact of popula- tion pressure and expansion of CRSL land were considerable. The trend of LULC dynamics in the study watershed implies adverse impact on the quality and quantity of the land resource. Hence, appropriate land use planning and strategies that reduce expansion of cultivated land need to be practiced

Precocious Natural Mummification in a Temperate Climate (Western Cape, South Africa)

The general process and pattern of decomposition is well-documented and understood. However, specific environmental conditions may alter this pattern and prematurely terminate the decay process. An example of this is natural mummification – a preservative process characterized by desiccation, brittleness and shrinkage of the skin and body tissues. It is important to understand how, when, and where such variations may occur, and for this reason environmentally-specific studies of decay are required. The aim of the present study was the establish baseline data on soft-tissue decomposition in two terrestrial habitats in the Western Cape. A total of 16 pig carcasses serving as analogues for humans were deployed in these habitats during two successive winters and summers between 2014 and 2016. The rate and pattern of decomposition were assessed via measurement of weight loss over time and scoring the decomposition process using Megyesi et al. (2005) Total Body Score system and study-specific criteria for mummification. Carcasses typically followed the expected pattern of decay with a few exceptions, most notably instances of rapid natural mummification. Natural mummification, as defined by Megyesi et al. (2005), was observed to occur as early as 17 days postmortem, with five carcasses mummifying in less than one month. The timing of natural mummification varies widely, from a few days to several years, averaging around three months in temperate regions. Natural mummification occurring in less than one month is termed precocious mummification and is rarely observed in temperate regions. With only three reports globally, this study’s findings are globally significant, highlighting the importance of regionally-specific decomposition studies. Two local forensic cases wherein precocious mummification has been observed are also presented and, considered together with the study’s results, a possible mechanism driving this process is proposed