Editor's choice: selected new literature April 2017
  • Soil: The Forgotten Piece of the Water, Food, Energy Nexus.
  • Conserving wild Arabica coffee: Emerging threats and opportunities.
  • An Assessment of Genetic Diversity and Drought Tolerance in Argan Tree (Argania spinosa) Populations: Potential for the Development of Improved Drought Tolerance.
  • Development and validation of risk profiles of West African rural communities facing multiple natural hazards.
  • Continuous and consistent land use /cover change estimates using socio-ecological data.
  • Climate change impact in the Western Himalaya: people's perception and adaptive strategies.
  • Characterization of Faidherbia albida (Del.) A. Chev. population in agroforestry parklands in the highlands of Northern Ethiopia : impact of conservation, environmental factors and human disturbances.
  • Nitrogen turnover and greenhouse gas emissions in a tropical alpine ecosystem, Mt. Kilimanjaro , Tanzania.
  • Biodiversity Areas under Threat: Overlap of Climate Change and Population Pressures on the World's Biodiversity Priorities.
  • Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes.
  • Using remotely sensed temperature to estimate climate response functions.
  • Global gross primary productivity and water use efficiency changes under drought stress.

Soil: The Forgotten Piece of the Water, Food, Energy Nexus.

Jerry L. Hatfield, Thomas J. Sauer, Richard M. Cruse (2017). Advances in Agronomy, Available online 15 March 2017.03.247

Abstract: The water, food, energy nexus has prompted sustainability concerns as interactions between these interdependent human needs are degrading natural resources required for a secure future world. Discussions about the future needs for food, water, and energy to support the increasing world population have ignored our soil resource that is the cornerstone or our capacity to produce food, capture water, and generate energy from biological systems. Soil scientists often recognize soils as a critical component of food, energy, or water security; however, the translation of that awareness into action strategies to either enhance public recognition of soil resource importance or improve soil management is lacking. Food, water, and energy security represents the current and future challenge of sustaining humankind while protecting the environment. These interactions are recognized by scientists, but the linkage to policy decisions or implementation of strategies to create positive outcomes for food, energy, or water enhancement is lacking. If we consider that soil is responsible for 99% of the world's food production, then the importance of soil in the food, energy, water nexus becomes apparent. If we further consider that soil erosion is the major factor, affecting soil degradation and declines in productivity are directly related to degradation of the soil resource, then the implications of soil in the context of increasing food, energy, and water security becomes more evident. However, if the attitude is one that technology will provide answers to these problems, then the soil degradation rate will continue to increase and we will reach a tipping point in which technological advances will not be able to overcome the impacts of a reduced topsoil depth coupled with a more variable climate. Soil is the forgotten piece of the food, energy, water nexus; however, the oversight extends beyond this nexus to include many of the ecological services required by humankind.

Conserving wild Arabica coffee: Emerging threats and opportunities.

Aerts, R; Geeraert, L; Berecha, G; Hundera, K; Muys, B; De Kort, H; Honnay, O 92017). AGRICULTURE ECOSYSTEMS & ENVIRONMENT, 237 75-79; 10.1016/j.agee.2016.12.023 JAN 16 2017

201704 literature1Abstract: Climate change and emerging pests and diseases are posing important challenges to global crop productivity, including that of Arabica coffee. The genetic basis of commercially used Arabica coffee cultivars are extremely narrow, and it is uncertain how much genetic diversity is present in ex situ collections. Conserving the wild Arabica coffee gene pool and its evolutionary potential present in the montane forests of SW Ethiopia is thus critically important for maintaining coffee yield and yield stability worldwide. Globally, coffee agroforestry helps to conserve forest cover and forest biodiversity that cannot persist in open agricultural landscapes, but the conservation of the wild Arabica coffee gene pool requires other priorities than those that are usually set for conserving forest biodiversity in mixed tropical landscapes. We show how forest loss and degradation, coffee management, in particular production intensification, and the introduction of cultivars, are threatening the genetic integrity of these wild populations. We propose an active land sparing approach based on strict land use zoning to conserve the genetic resources and the in situ evolutionary potential of Arabica coffee and discuss the major challenges including the development of access and benefit sharing mechanisms for ensuring long-term support to conservation.

An Assessment of Genetic Diversity and Drought Tolerance in Argan Tree (Argania spinosa) Populations: Potential for the Development of Improved Drought Tolerance.

Chakhchar, A; Haworth, M; El Modafar, C; Lauteri, M; Mattioni, C; Wahbi, S; Centritto, M.(2017). FRONTIERS IN PLANT SCIENCE, 8 1-11; 10.3389/fpls.2017.00276 MAR 2 2017

201704 literature3Abstract: The argan tree (Argania spinosa) occurs in a restricted area of Southwestern Morocco characterized by low water availability and high evapotranspirative demand. Despite the adaptation of the argan tree to drought stress, the extent of the argan forest has declined markedly due to increased aridity, land use changes and the expansion of olive cultivation. The oil of the argan seed is used for cooking and as the basis for numerous cosmetics. The identification of argan tree varieties with enhanced drought tolerance may minimize the economic losses associated with the decline of the argan forest and constrain the spread of desertification. In this study we collected argan ecotypes from four contrasting habitats and grew them under identical controlled environment conditions to investigate their response to drought. Leaf gas exchange analysis indicated that the argan ecotypes showed a high degree of adaptation to drought stress, maintaining photosynthetic activity at low levels of foliar water content and co-ordinating photosynthesis, stomatal behavior and metabolism. The stomata of the argan trees were highly sensitive to increased leaf to air vapour pressure deficit, representing an adaptation to growth in an arid environment where potential evapotranspiration is high. However, despite originating in contrasting environments, the four argan ecotypes exhibited similar gas exchange characteristics under both fully irrigated and water deficit conditions. Population genetic analyses using microsatellite markers indicated a high degree of relatedness between the four ecotypes; indicative of both artificial selection and the transport of ecotypes between different provinces throughout centuries of management of the argan forest . The majority of genetic variation across the four populations (71%) was observed between individuals, suggesting that improvement of argan is possible. Phenotypic screening of physiological responses to drought may prove effective in identifying individuals and then developing varieties with enhanced drought tolerance to enable the maintenance of argan production as climate change results in more frequent and severe drought events in Northern Africa .

Development and validation of risk profiles of West African rural communities facing multiple natural hazards.

Asare-Kyei, D; Renaud, FG; Kloos, J; Walz, Y; Rhyner, J (2017). PLOS ONE, 12 (3):10.1371/journal.pone.0171921 MAR 1 2017

Abstract: West Africa has been described as a hotspot of climate change . The reliance on rain-fed agriculture by over 65% of the population means that vulnerability to climatic hazards such as droughts, rainstorms and floods will continue. Yet, the vulnerability and risk levels faced by different rural social-ecological systems (SES) affected by multiple hazards are poorly understood. To fill this gap, this study quantifies risk and vulnerability of rural communities to drought and floods. Risk is assessed using an indicator-based approach. A stepwise methodology is followed that combines participatory approaches with statistical, remote sensing and Geographic Information System techniques to develop community level vulnerability indices in three watersheds (Dano, Burkina Faso; Dassari, Benin; Vea, Ghana ). The results show varying levels of risk profiles across the three watersheds. Statistically significant high levels of mean risk in the Dano area of Burkina Faso are found whilst communities in the Dassari area of Benin show low mean risk. The high risk in the Dano area results from, among other factors, underlying high exposure to droughts and rainstorms, longer dry season duration, low caloric intake per capita, and poor local institutions. The study introduces the concept of community impact score (CIS) to validate the indicator-based risk and vulnerability modelling. The CIS measures the cumulative impact of the occurrence of multiple hazards over five years. 65.3% of the variance in observed impact of hazards/CIS was explained by the risk models and communities with high simulated disaster risk generally follow areas with high observed disaster impacts. Results from this study will help disaster managers to better understand disaster risk and develop appropriate, inclusive and well integrated mitigation and adaptation plans at the local level. It fulfils the increasing need to balance global/regional assessments with community level assessments where major decisions against risk are actually taken and implemented.

Continuous and consistent land use /cover change estimates using socio-ecological data.

Marshall, M; Norton-Griffiths, M; Herr, H; Lamprey, R; Sheffield, J; Vagen, T; Okotto-Okotto, J (2017). EARTH SYSTEM DYNAMICS, 8 55-73; 10.5194/esd-8-55-2017 FEB 8 2017

Abstract: A growing body of research shows the importance of land use /cover change (LULCC) on modifying the Earth system. Land surface models are used to stimulate land atmosphere dynamics at the macro scale, but model bias and uncertainty remain that need to be addressed before the importance of LULCC is fully realized. In this study, we propose a method of improving LULCC estimates for land surface modeling exercises. The method is driven by projectable socio-ecological geospatial predictors available seamlessly across sub-Saharan Africa and yielded continuous (annual) estimates of LULCC at 5 km x 5 km spatial resolution. The method was developed with 2252 sample area frames of 5 km x 5 km consisting of the proportion of several land cover types in Kenya over multiple years. Forty three socio-ecological predictors were evaluated for model development. Machine learning was used for data reduction, and simple (functional) relationships defined by generalized additive models were constructed on a subset of the highest ranked predictors (p <= 10) to estimate LULCC. The predictors explained 62 and 65% of the variance in the proportion of agriculture and natural vegetation, respectively, but were less successful at estimating more descriptive land cover types. In each case, population density on an annual basis was the highest ranked predictor. The approach was compared to a commonly used remote sensing classification procedure, given the wide use of such techniques for macro scale LULCC detection, and outperformed it for each land cover type. The approach was used to demonstrate significant trends in expanding (declining) agricultural (natural vegetation) land cover in Kenya from 1983 to 2012, with the largest increases (declines) occurring in densely populated high agricultural production zones. Future work should address the improvement (development) of existing (new) geospatial predictors and issues of model scalability and transferability.

Climate change impact in the Western Himalaya: people's perception and adaptive strategies.

Negi, VS; Maikhuri, RK; Pharswan, D; Thakur, S; Dhyani, PP (2017). JOURNAL OF MOUNTAIN SCIENCE, 14 (2):403-416; 10.1007/s11629-015-3814-1 FEB 2017

Abstract: The Himalaya represents a vast mountain system and globally valued for its significant role in regulation of global as well as regional climate that has direct impact on biodiversity and ecosystem services crucial for sustenance of millions of people in Himalaya and adjoining areas. However, mountain regions worldwide are impacted by climate change and at the same time represent distinctive area for the assessment of climate related impacts. Climate change impacts in Himalayan region have its implications on food production, natural ecosystems, retreat of glacier, water supply, human and animal health and overall human wellbeing. The livelihood and food security of the people inhabited in region largely depend on climate sensitive sectors i.e. agriculture, livestock, forestry and their interlinkages with each other, and has the potential to break down food and nutritional security as well as livelihood support systems. People's perception and understanding of climate can be an important asset when it comes to adaptation to climate change impact; however it is not taken into consideration for the development of policy design and implementation of modern mitigation and adaptation strategies by governments and other civil society organizations. The knowledge of local people and farming communities for rural landscape management and sustainable use of bioresources is gaining credence as a key strategy to cope up with the climate change . Therefore, the present study analyzes the indigenous knowledge of local people and their perceptions on climate change , and also documented adaptation approaches at local level in mountain ecosystem of western Himalaya. The study could be useful to policy makers to design appropriate adaptation strategies to cope up with the impacts of climate change .

Characterization of Faidherbia albida (Del.) A. Chev. population in agroforestry parklands in the highlands of Northern Ethiopia : impact of conservation, environmental factors and human disturbances.

Noulekoun, F; Birhane, E; Chude, S; Zenebe, A (2017). AGROFORESTRY SYSTEMS, 91 (1):123-135; 10.1007/s10457-016-9910-6 FEB 2017

Abstract: Concerns about sustainable management and conservation of multipurpose trees in their habitat have led to increased number of studies on the ecological characterization of their population. Such knowledge on Faidherbia albida, the most used tree in agroforestry parklands in Ethiopia, is limited. F. albida population was characterized in and compared between two agroforests having different conservation status in Northern Ethiopia. Population structural parameters along with environmental factors and human activities were assessed in 42 randomly installed plots using a transect method. Size class distribution was used to describe and analyze the species long-term population dynamics. Adult density was almost three times higher in Zongi agroforest (19.9 +/- 2.9 trees ha(-1)) where the species has been conserved and managed for longer time compared to Abraha-atsbeha agroforest (7.9 +/- 2.5 trees ha(-1)). The same trend was observed for tree morphological parameters which were significantly higher at Zongi than Abraha-atsbeha. However, size class distributions coefficient of skewness and the median diameter indicated a declining and vulnerable population at Zongi and an increasing population at Abraha-atsbeha. Species population characteristics were influenced by environmental factors such as altitude, stone cover, erosion severity, slope, and human-related disturbances including land use , fodder harvesting, distance away from the center of the village and proximity of household to the plots. The study confirms the impact of conservation, environmental factors and human disturbances on shaping F. albida population and recommends the consideration of the trade-offs between them to design effective conservation and management strategies to sustain F. albida agroforests.

Nitrogen turnover and greenhouse gas emissions in a tropical alpine ecosystem, Mt. Kilimanjaro , Tanzania.

Gutlein, A; Zistl-Schlingmann, M; Becker, JN; Cornejo, NS; Detsch, F; Dannenmann, M; Appelhans, T; Hertel, D; Kuzyakov, Y; Kiese, R (2017). PLANT AND SOIL, 411 (1-2):243-259; 10.1007/s11104-016-3029-4 FEB 2017

201704 literature3Abstract: Tropical alpine ecosystems are identified as the most vulnerable to global environmental change , yet despite their sensitivity they are among the least studied ecosystems in the world. Despite its important role in constraining potential changes to the carbon balance, soil nitrogen (N) turnover and plant availability in high latitude and high altitude ecosystems is still poorly understood. Here we present a first time study on a tropical alpine Helichrysum ecosystem at Mt. Kilimanjaro , Tanzania , which lies at an altitude of 3880 masl. Vegetation composition is characterized and major gross N turnover rates are investigated using the N-15 pool dilution method for three different vegetation cover types. In addition greenhouse gas exchange (CO2, N2O and CH4) was manually measured using static chambers. Gross N turnover rates and soil CO2 and N2O emissions were generally lower than values reported for temperate ecosystems, but similar to tundra ecosystems. Gross N mineralization, NH4 (+) immobilization rates, and CO2 emissions were significantly higher on densely vegetated plots than on sparsely vegetated plots. Relative soil N retention was high and increased with vegetation cover, which suggests high competition for available soil N between microbes and plants. Due to high percolation rates, irrigation/rainfall has no impact on N turnover rates and greenhouse gas (GHG) emissions. While soil N2O fluxes were below the detection limit at all plots, soil respiration rates and CH4 uptake rates were higher at the more densely vegetated plots. Only soil respiration rates followed the pronounced diurnal course of air and soil temperature. Overall, our data show a tight N cycle dominated by closely coupled ammonification-NH4 (+)-immobilization, which is little prone to N losses. Warming could enhance vegetation cover and thus N turnover; however, only narrower C:N ratios due to atmospheric nitrogen deposition may open the N cycle of Helichrysum ecosystems.

Biodiversity Areas under Threat: Overlap of Climate Change and Population Pressures on the World's Biodiversity Priorities.

Aukema, JE; Pricope, NG; Husak, GJ; Lopez-Carr, D (2017). PLOS ONE, 12 (1):10.1371/journal.pone.0170615 JAN 26 2017

Abstract: Humans and the ecosystem services they depend on are threatened by climate change . Places with high or growing human population as well as increasing climate variability, have a reduced ability to provide ecosystem services just as the need for these services is most critical. A spiral of vulnerability and ecosystem degradation often ensues in such places. We apply different global conservation schemes as proxies to examine the spatial relation between wet season precipitation, population change over three decades, and natural resource conservation. We pose two research questions: 1) Where are biodiversity and ecosystem services vulnerable to the combined effects of climate change and population growth? 2) Where are human populations vulnerable to degraded ecosystem services? Results suggest that globally only about 20% of the area between 50 degrees latitude North and South has experienced significant change-largely wetting-in wet season precipitation. Approximately 40% of rangelands and 30% of rainfed agriculture lands have experienced significant precipitation changes, with important implications for food security. Over recent decades a number of critical conservation areas experienced high population growth concurrent with significant wetting or drying (e.g. the Horn of Africa , Himalaya, Western Ghats, and Sri Lanka), posing challenges not only for human adaptation but also to the protection and sustenance of biodiversity and ecosystem services. Identifying areas of climate and population risk and their overlap with conservation priorities can help to target activities and resources that promote biodiversity and ecosystem services while improving human well-being.

Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes.

Pelster, D; Rufino, M; Rosenstock, T; Mango, J; Saiz, G; Diaz-Pines, E; Baldi, G; Butterbach-Bahl, K (2017). BIOGEOSCIENCES, 14 (1):187-202; 10.5194/bg-14-187-2017 JAN 12 2017

Abstract: Few field studies examine greenhouse gas (GHG) emissions from African agricultural systems, resulting in high uncertainty for national inventories. This lack of data is particularly noticeable in smallholder farms in sub-Saharan Africa , where low inputs are often correlated with low yields, often resulting in food insecurity as well. We provide the most comprehensive study in Africa to date, examining annual soil CO2, CH4 and N2O emissions from 59 smallholder plots across different vegetation types, field types and land classes in western Kenya . The study area consists of a lowland area (approximately 1200 m a.s.l.) rising approximately 600m to a highland plateau. Cumulative annual fluxes ranged from 2.8 to 15.0 Mg CO2-C ha(-1), -6.0 to 2.4 kg CH4-C ha(-1) and -0.1 to 1.8 kg N2O-N ha(-1). Management intensity of the plots did not result in differences in annual GHG fluxes measured (P =0.46, 0.14 and 0.67 for CO2, CH4 and N2O respectively). The similar emissions were likely related to low fertilizer input rates (<= 20 kg N ha(-1)). Grazing plots had the highest CO2 fluxes (P = 0.005), treed plots (plantations) were a larger CH4 sink than grazing plots (P =0.05), while soil N2O emissions were similar across vegetation types (P= 0.59). This study is likely representative for low fertilizer input, smallholder systems across sub-Saharan Africa , providing critical data for estimating regional or continental GHG inventories. Low crop yields, likely due to low fertilization inputs, resulted in high (up to 67 g N2O-N kg(-1) aboveground N uptake) yield scaled emissions. Improvement of crop production through better water and nutrient management might therefore be an important tool in increasing food security in the region while reducing the climate footprint per unit of food produced.

Using remotely sensed temperature to estimate climate response functions.

Heft-Neal, S; Lobell, DB; Burke, M (2017). ENVIRONMENTAL RESEARCH LETTERS, 12 (1):10.1088/1748-9326/aa5463 JAN 2017

Abstract: Temperature data are commonly used to estimate the sensitivity of many societally relevant outcomes, including crop yields, mortality, and economic output, to ongoing climate changes. In many tropical regions, however, temperature measures are often very sparse and unreliable, limiting our ability to understand climate change impacts. Here we evaluate satellite measures of near-surface temperature (Ts) as an alternative to traditional air temperatures (Ta) from weather stations,and in particular their ability to replace Ta in econometric estimation of climate response functions. We show that for maize yields in Africa and the United States, and for economic output in the United States, regressions that use Ts produce very similar results to those using Ta, despite the fact that daily correlation between the two temperature measures is often low. Moreover, for regions such as Africa with poor station coverage, we find that models with Ts outperform models with Ta, as measured by both R-2 values and out-of-sample prediction error. The results indicate that Ts can be used to study climate impacts in areas with limited station data, and should enable faster progress in assessing risks and adaptation needs in these regions.

Global gross primary productivity and water use efficiency changes under drought stress.

Yu, Z; Wang, JX; Liu, SR; Rentch, JS; Sun, PS; Lu, CQ (2017). ENVIRONMENTAL RESEARCH LETTERS, 12 (1):10.1088/1748-9326/aa5258 JAN 2017

Abstract: Drought can affect the structure, composition and function of terrestrial ecosystems, yet drought impacts and post-drought recovery potentials of different land cover types have not been extensively studied at a global scale. We evaluated drought impacts on gross primary productivity (GPP), evapotranspiration (ET), and water use efficiency (WUE) of different global terrestrial ecosystems, as well as the drought-resilience of each ecosystem type during the period of 2000 to 2011. Using GPP as biome vitality indicator against drought stress, we developed a model to examine ecosystem resilience represented by the length of recovery days (LRD). LRD presented an evident gradient of high (> 60 days) in mid-latitude region and low (< 60 days) in low (tropical area) and high (boreal area) latitude regions. As average GPP increased, the LRD showed a significantly decreasing trend, indicating readiness to recover after drought, across various land cover types (R 2 = 0.68, p < 0.0001). Moreover, zonal analysis revealed that the most dramatic reduction of the drought-induced GPP was found in the mid-latitude region of the Northern Hemisphere (48% reduction), followed by the low-latitude region of the Southern Hemisphere (13% reduction). In contrast, a slightly enhanced GPP (10%) was evident in the tropical region under drought impact. Additionally, the highest drought-induced reduction of ET was found in the Mediterranean area, followed by Africa . Water use efficiency, however, showed a pattern of decreasing in the Northern Hemisphere and increasing in the Southern Hemisphere. Drought induced reductions of WUE ranged from 0.96% to 27.67% in most of the land cover types, while the increases of WUE found in Evergreen Broadleaf Forest and savanna were about 7.09% and 9.88%, respectively. These increases of GPP and WUE detected during drought periods could either be due to water-stress induced responses or data uncertainties, which require further investigation.