5 links to more articles on climate change and Africa

Richard Rood's blog (December 9, 2010, entry: http://www.wunderground.com/blog/RickyRood/comment.html?entrynum=178) at wunderground contained the following links to information on climate change and Africa:

Climate variability and climate change: Impacts on Kenyan agriculture

A wonderful collection of stories on agriculture and climate change in Africa

Climate change as opportunity in Africa

Voice of America Coverage of African Climate Adaptation

Africa’s Growing Water Crisis

12 Million Egyptians to be Affected by Climate Change

12 Million Egyptians to be Affected by Climate Change

by Mohamed Abdel Salam, January 2, 2010 


Cairo: A study conducted by the Center for Remote Sensing at Boston University, commissioned by the Arab Forum for Environment and Development, warned that Egypt would be one of the Arab countries most affected by climate change. The study analyzed a variety of scenarios of climate change impact, particularly on coastal areas, based on satellite images of the region, and showed that Egypt would be the most affected Arab country due to a rise in sea levels. The study stated that, “at least 12 million Egyptians will be forced to migrate from their area of residence in parts of the Nile Delta and that with a rise in sea level of 5 meters, almost one third of the total affected Arab population would be Egyptian."

The study was prepared by Dr. Eman Ghoneim, a research professor at the Center for Remote Sensing, and devoted a large portion of its findings to the impact of rising sea levels in the Nile Delta. The study warned, “under the scenarios of rising sea levels, much of the Nile Delta would be lost forever, and the analysis by the remote sensing and geographic information system classified some areas in the Nile Delta at risk if sea levels rise by one meter.” The report estimated that a rise of only one meter could engulf much of the Nile Delta. With about one third of the Delta area underwater, some of its coastal cities, such as Alexandria, Edco, Port Said and Damietta, would be in great danger. Under this scenario, it is estimated that about 8.5% of the country’s population (7 million) would be forced to migrate to other areas.
The study added, “In the extreme case scenario of a 5-meter sea level rise, more than half of the Nile Delta (58%) will face devastating effects and 10 major cities would be threatened, including Alexandria, Damanhur, Kafr El-Sheikh, Damietta, Mansoura and Port Said. Rising water would drown productive plots of agricultural land and force about 14% of the country’s population (11.5 million) to move to areas of the more densely populated areas south of the Nile Delta region.”

The study went on to say that “the Nile Delta, which covers about 24,900 square kilometers, and accounts for about 65% of agricultural land in Egypt, was once the largest site for sediment deposits in the basin of the Mediterranean Sea. It is an extreme example of low, flat land located in an area that is very vulnerable to rising sea levels.” The Delta is threatened due to accelerated erosion of the coastline and the establishment of the Aswan High Dam in 1962, which subsequently sequestered large amounts of sediment behind the dam in Lake Nasser.

The study showed that coastal erosion of the Delta as a result of natural causes and the extraction of groundwater can be seen in satellite images, especially near the coastal cities of Rosetta and Damietta. The analysis of satellite images shows that the Ras Rashid “Rosetta” lost almost 9.5 square kilometers of area. Likewise, the coastline retreated 3 km in the last 30 years (1972-2003), meaning that this part of the Delta declined at the alarming rate of about 100 meters per year.

Study also discussed the consequences of climate change on the Arab region as a whole, including the impact of rising sea levels and its effects on the growth of cities, stating that the southern part of the Nile Delta is now suffering from uncontrolled population growth in the city of Cairo. The results also showed a loss of about 12% (62 square kilometers) of the agricultural areas adjacent to Cairo between 1984 and 2002.

Link:  http://bikyamasr.com/wordpress/?p=7325

Hydro-climatic trends and water resource management implications based on multi-scale data for the Lake Victoria region, Kenya

Environ. Res. Lett. 5 (July-September 2010) 034005;   doi:10.1088/1748-9326/5/3/034005

Hydro-climatic trends and water resource management implications based on multi-scale data for the Lake Victoria region, Kenya

A. J. Koutsouris, G. Destouni, J. Jarsjö and S. W. Lyon*

Bert Bolin Centre for Climatic Research, Department of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm, Sweden

*Correspondence e-mail: steve.lyon@natgeo.su.se

Received 4 June 2010, accepted 23 July 2010, published 6 August 2010

Unreliable rainfall may be a main cause of poverty in rural areas, such as the Kisumu district by Lake Victoria in Kenya. Climate change may further increase the negative effects of rainfall uncertainty. These effects could be mitigated to some extent through improved and adaptive water resource management and planning, which relies on our interpretations and projections of the coupled hydro-climatic system behaviour and its development trends. In order to identify and quantify the main differences and consistencies among such hydro-climatic assessments, this study investigates trends and exemplifies their use for important water management decisions for the Lake Victoria drainage basin (LVDB), based on local scale data for the Orongo village in the Kisumu district, and regional scale data for the whole LVDB. Results show low correlation between locally and regionally observed hydro-climatic trends, and large differences, which in turn affects assessments of important water resource management parameters. However, both data scales converge in indicating that observed local and regional hydrological discharge trends are primarily driven by local and regional water use and land use changes.

Keywords:  Lake Victoria, Kenya, hydrology, water resource management, irrigation, climate change, hydro-climatic interaction

1. Introduction

Climatic changes are likely to threaten the Earth's already scarce water supply. Currently, about 40%, or 2.8 billion people, of the world population live in river basins with water scarcity. Improved water resource management is needed to help mitigate the potential influence of climatic changes and better utilize current water supplies. For example, about 1.6 billion people live in areas where the water scarcity has resource, developmental or economic reasons (UN 2008). Economic water scarcity occurs when a lack of financial, human or institutional capital causes incapacity to utilize better otherwise sufficient water resources. Lack of water produces negative effects on food security, health, gender equality and education making it both directly and indirectly connected with many of the United Nations' millennium development goals. As lack of financial capital also limits the capacity to import virtual water, which could otherwise compensate for physical water scarcity, water scarcity is thus primarily a crisis of the poor (UN 2006) that will be exacerbated under climatic changes.

For example, Kenya currently uses only 9% of its available water resources (e.g., water resources that would be exploitable if no financial constraints were present) while approximately 50% of the total population is below the national poverty line (UNDP 2008,Swallow et al. 2007). In addition, physical water scarcity often occurs seasonally in Kenya due to unevenly distributed rainfall throughout the year. This creates local water scarcity in many regions of Kenya due to a combination of economical and physical water scarcity. In the Kisumu district, located by Lake Victoria, 53% of the people live below the poverty line with an unreliable rainfall pattern identified as one of the main causes through its effects on food security (NCAPD 2005). Though the mechanisms behind the poverty levels in rural Kenya are more complex than a cause-and-effect relationship between rainfall and poverty, rainfall patterns may exacerbate existing poverty due to the simple fact that many in rural Kenya are dependent on rain-fed agriculture. In the Kisumu district, approximately 90% of the population is dependent on agriculture for both food and income, causing a large part of the population to be affected directly by droughts and floods. Taken together with the strong seasonality in rainfall, the water resources in Kenya and the Kisumu district are quite sensitive to climatic trends. This is exemplified in Orongo village (figure 1) located in the Kisumu district. It is a typical rural, lowland floodplain area in Kenya and as such it is sensitive to the effects of rainfall variability and water management (Swallow et al. 2007). This makes Orongo village a focal point for the efforts of international assistance agencies (e.g., Engineers Without Borders) whose goals are to provide reliable and sustained water resources to the local population.

Figure 1. Site map showing the location of Lake Victoria and the spatial extent of the Lake Victoria drainage basin in Africa. The location of Orongo village near Kisumu is also indicated.

Climatic change may increase the negative effects of rainfall uncertainty, and both current and future effects of this uncertainty could be mitigated to some extent through improved and adaptive water resource management and planning. Planning for improved and more secure water availability relies on our interpretations and projections of the coupled hydro-climatic system behaviour. Better scientific understanding of hydrological and climatic links, conditions and changes is thus a key issue for effective water resource management and its climate adaptation, in Orongo village as in other parts of the Lake Victoria region (Swallow et al 2008) and other regions of the world.

Our understanding of the coupled hydro-climatic system may be greatly hindered by limitations in data availability and quality. For instance, trends identified on a local scale may differ significantly from trends based on regional scale data (see, e.g., Pielke et al2002 considering temperature in eastern Colorado, USA). This study compares such trend results and exemplifies their water management implications on the basis of local scale data from the Orongo village and regional scale data from the whole Lake Victoria drainage basin (LVDB). The main aims of this analysis are to further investigate the prevalence of hydro-climatic trend differences on the basis of data with differing resolution and on different scales, and the propagation of such differences to important water management parameters, such as water storage requirements. In addition to such differences, this study also aims to investigate potential important consistencies in hydro-climatic system trend assessments, which are robust against the use of differently resolved and quantified data on different scales.

2. The study area and data set descriptions

2.1.  Regional scale: the Lake Victoria drainage basin

Lake Victoria is located in East Africa, southwest of Africa's horn (figure 1), from 31°39 'E to 34°53 'E longitude and 0°20 'N to 3°00 'S latitude. The lake is close to rectangular in shape with an area of around 67 000 km². The shoreline of the lake is divided between Uganda, Kenya and Tanzania. The water surface level is typically 1140 m above sea level and the lake has a mean depth of 40 m with a maximum depth of around 80–90 m. The LVDB has a land area of about 194 000 km² (Tate et al 2004) and is inhabited by one of the densest and poorest rural populations of the world (UNESCO 2006), where many are subsistence farmers depending on rain-fed agriculture (Anyah et al 2008).

The climate in LVDB can be classified as equatorial with hot and humid conditions where the main climate drivers are easterly monsoons and the bimodal passing of the inter-tropical convergence zone (Anyah and Semazzi 2007). Mean annual precipitation is 1780 mm and mean annual evapotranspiration is 1537 mm (Nicholson et al 2000). Rainfall occurs mainly during two periods: the long rains in March, April and May; and the short rains in September, October and November. Severe droughts occur approximately every 3–4 years during the short rains, every 7–8 years during the hot dry season (December, January, and February), and every 5–8 years during the long rainy season (Awange et al 2008). Lake Victoria is mainly rain-fed with direct precipitation accounting for approximately 80% of the water inflow to the lake (Sutcliffe and Petersen 2007), and about 10% coming from five main tributaries, with the Kagera River being the main contributor. The remaining 10% comes from various small tributaries. The only significant outlet is the White Nile (Song et al 2004), where the outlet is regulated near Jinja pass (0°25 '21 ' 'N, 33°11 '45 ' 'E). Since 1954, discharge and lake levels have been regulated by the Nalubaale dam (formerly known as the Owen Falls dam).

Data series of temperature and precipitation values at the regional scale of the LVDB were compiled from the spatially distributed CRU TS 2.1 Global Climate Data Set (Mitchell and Jones 2005). Temperature and precipitation data were available for monthly time steps from 1901 to 2002. The spatial extent of LVDB was delineated in ArcGIS 9.3^® using the hydrology toolbox and the SRTM 90 digital terrain model (Jarvis et al 2008). Regional scale, basin averages of the annual time series of spatially distributed temperature and precipitation data were calculated for the entire LVDB. The temperature time series was then used to estimate annual actual evapotranspiration from the LVDB area (see the supplementary data available at stacks.iop.org/ERL/5/034005/mmedia). Annual discharge data for Lake Victoria at Jinja pass were obtained from the Global hydro-climatic data network data set (Dettinger and Diaz 2000).

2.2.  Local scale: Orongo village

Orongo village is located near the coast of Lake Victoria within Kenyan territory (figure 1). It is located east of the Winam Gulf and 6 km southeast of Kisumu, the third largest city in Kenya. Orongo village is characterized by pastures, homesteads and subsistence farming. The village has about 3000 inhabitants and an effective population density of 600 people per km² (Levicki 2005). Two rivers flank Orongo village: Luanda River in the southeast and Nyamasaria River in the northwest. These rivers have their origin in the Nandi Escarpments which serve as the main recharge area for the region, having elevations up to approximately 1900 m. The lower parts of this region make up a part of the Kano Plains. Elevation in this lower section, a characteristically lowland floodplain with flat topography and minimal slope, ranges between 1140 and 1300 m. The principal soil types in the Kano Plains are histosols and vertisols (Onyango et al 2005). The land cover in this area is dominated by marshlands and subsistence agriculture (with maize and millet as the main crops).

Water Resources Management Affairs, Kenya (WRMA), have conducted stream flow observations approximately 30 km northeast from Orongo village. This neighbouring watershed, called the Little Oroba watershed, is the closest reliable stream gauge for Orongo village. The outlet of the 54 km² Little Oroba watershed is located at 34°58 '15 ' 'E, 0°01 '40 ' 'N. Continuous stream flow data are available for daily intervals from 1932 to 1999. These observations were used to calculate a time series of the local scale average annual stream flow from 1932 to 1999. In addition, daily observations of pan evaporation and precipitation measurements are made near Kisumu by WRMA. Pan evaporation data were used to estimate actual evapotranspiration at this local scale (see the supplementary data available at stacks.iop.org/ERL/5/034005/mmedia). These time series were averaged to obtain average annual time series of evapotranspiration and precipitation over the periods of record. Note that the temperature data are collected by Kenya meteorological department at Kisumu, but that this data set was not available for consideration in this study.

3. Methods

3.1.  Hydro-climatic trend analysis

Simple linear regression was used to analyse the trends in the time series of hydro-climatic data collected at both the local scale and the regional scale. These data include observed precipitation and river discharge, and estimated actual evapotranspiration, which in turn depends on temperature, based on two different methods for the local scale and the regional scale assessments (see the supplementary data available at stacks.iop.org/ERL/5/034005/mmedia).

To allow for direct comparison between the different time series, linear regressions were applied to all the data and time series for the period 1968–1995. During this period, all hydro-climatic data have overlapping observation records at both the local scale and the regional scale. The present analysis thus facilitates a direct trend comparison between the local scale and the regional scale hydro-climatic observations and calculations.

3.2.  Use of trend analysis for water management

In order to exemplify the trend analysis use for concrete water management purposes, we estimated the minimum water storage requirement for an average farmer in the region using both regional scale and local scale data. Minimum storage requirement is defined here as the crop water required under standard climatic conditions. The method used to estimate minimum storage requirement was a sequent peak algorithm (Bouver 1978). The sequent peak algorithm is a graphical method based on the cumulative sum of precipitation surplus (PS) defined as inflow minus outflow and demand. Assuming that inflow is due primarily to direct precipitation, outflow is the water lost due to evaporation, and demand is the water transpired by crops (i.e., losses due to leakage and irrigation inefficiency are assumed relatively small and negligible), the cumulative sum of precipitation surplus PS can be estimated as

where P is precipitation and ET_a is the actual evapotranspiration (evaporation plus transpiration by crops) for each time step t over a record of observation that is n time steps in length. Note that as the demand and outflow may be larger than the inflow, P – ET_a may be negative.

The sequent peak algorithm is applied to create a time series of cumulative PS. By plotting such a time series, the first peak and the following sequent peak that is higher than the first peak can be identified. The difference between the first-peak value and the minimum value before the sequent peak in time is the water storage requirement for that particular period. This procedure is carried out for the whole record of data at all peaks, and the largest difference found is then the minimum storage required to ensure sufficient water availability. While fairly basic, the sequent peak algorithm provides at least a first-order estimate of water storage requirements, which is compared here between the different scale data for the example of the average farmer of the Orongo village of the Kisumu district.

4. Results

4.1.  Hydro-climatic trends

Considering the precipitation data at the regional scale (figure 2(A)) and local scale (figure 2(B)), neither time series indicates any significant linear trend for the period 1968–1995. If the entire record of data available at both spatial scales is considered, this result holds and neither time series indicates any significant linear trends. Similar to precipitation records, estimated actual evapotranspiration at the regional scale (figure 2(C)) and that at the local scale (figure 2(D)) show no significant linear trend during the period 1968–1995. Again this lack of significant linear trend holds when considering the entire length of record at both scales.

Figure 2. Time series of annual regional scale precipitation (A), actual evapotranspiration (C), and discharge (E) data, and local scale precipitation (B), actual evapotranspiration (D), and discharge (F) data considered in this study. Trend lines shown are fitted for the period 1968–1995, over which all hydro-climatic data are available at both spatial scales.

With regard to regional discharge, however, there is a significant (p  <  0.05) negative linear trend over the period 1968–1995, following a period of increasing discharge at the outlet of Lake Victoria from 1959 to 1964 (figure 2E). In 1964 the discharge peaks and shifts to the significant negative trend. This shift excludes the application of a meaningful single linear regression analysis over the entire period of discharge observation. These results are consistent with previous studies of Lake Victoria's lake levels, showing a water level increase that peaks in the early 1960s (see e.g. Piper et al 1986, Mistry & Conway 2003) and then a decrease through to 2005 (see e.g., Mangeni 2006, Awange et al 2008).

Furthermore, while the regional scale discharge data show a significant negative linear trend from 1968 to 1995, the local scale discharge data (figure 2(F)) at the Little Oroba gauging station indicate a significant (p  <  0.05) positive linear trend in discharge during the 1968–1995 period. This trend is also seen when considering the entire length of record.

4.2.  Water storage requirements

The largest water deficit estimate using the sequent peak algorithm based on the regional scale data occurs during the period 1999–2001 (figure 3). From this deficit, the estimated minimum storage requirement for an average farmer in the region is 205 mm. Using local scale data within the sequent peak algorithm, the largest water deficit occurs during the period 1989–1994, with a minimum storage requirement of 592 mm. That is, an estimated water storage requirement based on local scale data nearly three times as large as that based on regional scale data.

Figure 3. Results from the sequent peak algorithm using an annual time step. The difference between the two sets of paired dashed lines shows the difference in estimated storage requirement based on regional scale and local scale data.

These minimum storage assessments can further be used to estimate the number of irrigation ponds needed to meet the storage requirements of the average farmer in the Orongo village. For example, Engineers Without Borders assumes that a typical irrigation pond in this region should have the dimensions of 15 m × 20 m × 2 m or about 600 m³ of storage (Levicki 2009). Using this design recommendation, the regional scale estimate of minimum storage translates into a requirement of about two irrigation ponds per acre of agricultural land. Using the local scale data, however, four irrigation ponds per acre of agricultural land are needed. There is, thus, a large influence of the choice of spatial hydro-climatic data resolution on the practical water resource management and planning for the example of Orongo village in the Kisumu district.

The large difference in estimated storage requirements may be partly due to the use of two different methods for estimating actual evapotranspiration at the local scale and the regional scale (see the supplementary data available atstacks.iop.org/ERL/5/034005/mmedia). The use of different methods, however, is not an independent choice, but a necessity due to differences in data resolution and availability at the two scales. It is often the case that available data dictate which methods can be used to determine unobserved hydro-climatic parameters such as evapotranspiration for use in estimates of water storage requirements.

5. Discussion and conclusion

There is clear disparity between discharge observations at the regional and local scales considered in this study, leading to different hydrological trend assessments based on the data from the different scales. The present results further exemplify and quantify how this disparity leads to large differences in the essential parameter of water storage requirement for provision of reliable and sustained water resources.

The inherent influence of data resolution and scale on the choices of quantification methods for water resource management assessments, as discussed above for the evapotranspiration quantification, is not often considered. This is probably because real-world water resource managers must often make decisions regardless of data availability limitations. Still, it is important to consider the effects of these limitations and associated implicit assumptions and generalizations, when managers are confronted with serious water management and climate-adaptation problems. These effects may be significant for resulting decisions and designs of water resource management options, particularly in hydro-climatically sensitive regions.

In the present results, however, we have also seen one important consistent aspect of regional scale and local scale discharge data implications: during the period of significant trends in inter-annual hydrological discharge (even though the trends are opposite on the different data scales), there are no significant trends evident in the climate variables precipitation and evapotranspiration, with the latter in turn depending on temperature. This aspect indicates that neither the regional nor the local trends in the inter-annual discharge changes are currently climate driven. Rather, the current observed discharge trends are most probably connected to local and regional water use and land use changes. This is consistent with the major land use changes, such as deforestation and agricultural expansion, and population growth observed in Lake Victoria drainage basin (Odada et al 2009, Lung and Schaab 2010). This development is not homogeneous within the drainage basin and is mainly seen along rivers and in coastal areas (agricultural expansion and population growth) and in the tropical forest (deforestation). This supports the disconnection between climate trends and discharge trends due to local and regional water use and land use changes.

For example, the recent negative regional discharge trend may be an effect of water regulation and management practices at the Nalubaale dam. Direct quantification of the effects of dams and other local/regional water management practices are outside the scope of the present study. However, such effects have been investigated in detail and led to similar conclusions for other hydro-climatically sensitive parts of the world, such as the Central Asian region of the Aral Sea drainage basin (Shibuo et al 2007). In addition, locally driven changes in discharge, in the absence of observable changes in climatic variables, have also been observed in other hydrological catchments in eastern Africa, for instance in Ethiopia (Collick et al 2009).

While the current climatic trends show little direct influence on discharge trends (regardless of data resolution and scale), there is potential for future climate change to influence water availability in this region. Relevant identification of such large scale climate change effects must then be based on realistic assessments also of the water cycling effects of local/regional water use and land use, in hydrological catchments of scales that are consistent with the specific water management problems and decisions.

Link to rest of paper:  http://iopscience.iop.org/1748-9326/5/3/034005/fulltext

Cheryl A. Palm et al., PNAS, Identifying potential synergies and trade-offs for meeting food security and climate change objectives in sub-Saharan Africa

Proc. Natl. Acad. Sci., published online before print May 7, 2010; doi: 10.1073/pnas.0912248107

Identifying potential synergies and trade-offs for meeting food security and climate change objectives in sub-Saharan Africa

 Cheryl A. Palm et al.

Abstract

Potential interactions between food production and climate mitigation are explored for two situations in sub-Saharan Africa, where deforestation and land degradation overlap with hunger and poverty. Three agriculture intensification scenarios for supplying nitrogen to increase crop production (mineral fertilizer, herbaceous legume cover crops—green manures—and agroforestry—legume improved tree fallows) are compared to baseline food production, land requirements to meet basic caloric requirements, and greenhouse gas emissions. At low population densities and high land availability, food security and climate mitigation goals are met with all intensification scenarios, resulting in surplus crop area for reforestation. In contrast, for high population density and small farm sizes, attaining food security and reducing greenhouse gas emissions require mineral fertilizers to make land available for reforestation; green manure or improved tree fallows do not provide sufficient increases in yields to permit reforestation. Tree fallows sequester significant carbon on cropland, but green manures result in net carbon dioxide equivalent emissions because of nitrogen additions. Although these results are encouraging, agricultural intensification in sub-Saharan Africa with mineral fertilizers, green manures, or improved tree fallows will remain low without policies that address access, costs, and lack of incentives. Carbon financing for small-holder agriculture could increase the likelihood of success of Reducing Emissions from Deforestation and Forest Degradation in Developing Countries programs and climate change mitigation but also promote food security in the region.

Link:  http://www.pnas.org/content/early/2010/06/16/0912248107.abstract

Hiroaki Kawase et al., GRL 37 (2010), Physical mechanism of long-term drying trend over tropical North Africa

Geophysical Research Letters, 37 (2010) L09706; doi: 10.1029/2010GL043038 

Physical mechanism of long-term drying trend over tropical North Africa

Physical mechanism of long-term drying trend over tropical North Africa

Hiroaki Kawase, Manabu Abe, Yukiko Yamada (National Institute for Environmental Studies, Tsukuba, Japan), Toshihiko Takemura (Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan), Tokuta Yokohata (Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan) and Toru Nozawa (National Institute for Environmental Studies, Tsukuba, Japan)

Abstract

Based on an approximated moisture budget equation, we investigate the physical mechanisms of a drying trend observed over tropical North Africa in the boreal summer during the 20th Century by analyzing datasets of several climate-model experiments forced with various combinations of natural and anthropogenic forcings. Increased anthropogenic aerosols thermodynamically induce a drying trend due to a tropospheric cooling and dynamically induce an additional drying trend due to an atmospheric local circulation change stirred up by the strong gradient of a sea surface temperature anomaly over the tropical Atlantic Ocean. Increased greenhouse gases, on the other hand, induce a drying trend through the large-scale dynamic effect, which is canceled out by the thermodynamically induced moistening trend due to tropospheric warming. Therefore, the drying trend observed over tropical North Africa during the 20th Century is strongly affected by the increased anthropogenic aerosols through both the dynamic and thermodynamic effects. 

Received 4 March 2010; accepted 31 March 2010; published 11 May 2010.

Link:  http://www.agu.org/pubs/crossref/2010/2010GL043038.shtml

Unprecedented Warming in East Africa's Lake Tanganyika; Lake's surface waters are warmest in 1,500 years

Unprecedented Warming in East Africa's Lake Tanganyika

Lake's surface waters are warmest on record

Local fishermen troll the waters of Lake Tanganyika, catching sardines--for now.

National Science Foundation, May 16, 2010

Lake Tanganyika, the second-oldest and second-deepest lake in the world, could be in for some rough waters.

Geologists have determined that the East African rift lake has experienced unprecedented warming during the last century; its surface waters are the warmest on record.

That finding is important, the scientists state in this week's on-line issue of the journal Nature Geoscience, because the warm surface waters likely will affect fish stocks upon which millions of people in the region depend.

"This result is in addition to those from other African lakes showing that changes in regional climate have a significant impact on the lakes, and on the human populations that depend on the lakes' resources," said Paul Filmer, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

The scientists took core samples from the lakebed that laid out a 1,500-year history of the lake's surface temperature.

The resulting data showed that the lake's surface temperature, 26 °C (78.8 °F), last measured in 2003, is the warmest the lake has been for a millennium and a half.

The team also documented that Lake Tanganyika experienced its largest temperature change in the 20th century. The change has affected its unique ecosystem, which relies upon nutrients from the depths to jumpstart the food chain on which fish survive.

"Our data show a consistent relationship between lake surface temperature and productivity such as that of fish stocks," said Jessica Tierney of Brown University, the paper's lead author. "As the lake gets warmer, we expect productivity to decline, and we expect that it will affect the fishing industry."

Cores were taken in 2001 by Andrew Cohen, a geologist at the University of Arizona, and in 2004 by James Russell, a geologist at Brown University.

Lake Tanganyika is bordered by Burundi, the Democratic Republic of Congo, Tanzania, and Zambia--four of the poorest countries in the world.

An estimated 10 million people live near the lake, and depend on it for drinking water and for food.

Fishing is a crucial component of their diets and livelihoods: up to 200,000 tons of sardines and four other fish species are harvested annually from Lake Tanganyika.

The lake, one of the richest freshwater ecosystems in the world, is divided into two levels. Most of the animal species live in the upper 100 meters, including valuable sardines.

Below that, the lake holds less and less oxygen, and at certain depths, it has no oxygen.

The lake depends on wind to churn its waters and send nutrients from the depths toward the surface. These nutrients are food for algae, which supports the lake's entire food web.

But as Lake Tanganyika warms, the mixing of waters is lessened; fewer nutrients are funneled from the depths to the surface.

More warming at the surface magnifies the difference between the two lake levels; even more wind is needed to churn the waters enough to ferry nutrients toward the upper layer.

The researchers' data show that during the last 1,500 years, intervals of prolonged warming and cooling are linked with low and high algal productivity, respectively, indicating a clear link between past temperature changes and biological productivity in the lake.

"People throughout south-central Africa depend on the fish from Lake Tanganyika as a crucial source of protein," Cohen said. "This resource is likely threatened by the lake's unprecedented warming and the associated loss of lake productivity."

Climate change models show a general warming trend in the region, which would cause even greater warming of Lake Tanganyika's surface waters.

Some researchers believe that the declining fish stocks in Lake Tanganyika can be attributed mainly to overfishing, and Tierney and Russell say that may be a reason.

But they note that the warming in the lake, and the lessened mixing of critical nutrients, is exacerbating the fish stocks' decline, if not causing it.

"It's almost impossible for it not to be," Russell said.

Media Contacts Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Richard Lewis, Brown University (401) 863-3766 richard_lewis@brown.edu


The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

Link:  http://www.nsf.gov/news/news_summ.jsp?cntn_id=116956&WT.mc_id=USNSF_51&WT.mc_ev=click

J. E. Tierney et al., Nature Geosci., (2010), Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500

Nature Geoscience, published online 16 May 2010; doi: 10.1038/ngeo865

Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500

Jessica E. Tierney* (Brown University Department of Geological Sciences, Box #1846, Providence, RI 02912, U.S.A.), Marc T. Mayes (Brown University Department of Geological Sciences, Box #1846, Providence, RI 02912, U.S.A., and Center for Sustainability and the Global Environment, Nelson Institute for Environmental Studies, University of Wisconsin-Madison, 1710 University Ave., Madison, WI 53726, U.S.A.), Natacha Meyer (Brown University Department of Geological Sciences, Box #1846, Providence, RI 02912, U.S.A.), Christopher Johnson (Department of Geosciences, University of Arizona, 1040 E 4th St., Tucson, AZ 85721, U.S.A., and Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, U.S.A.), Peter W. Swarzenski (United States Geological Survey, 400 Natural Bridges Drive, Santa Cruz, CA 95060, U.S.A.), Andrew S. Cohen (Department of Geosciences, University of Arizona, 1040 E 4th St., Tucson, AZ 85721, U.S.A.) and James M. Russell (Brown University Department of Geological Sciences, Box #1846, Providence, RI 02912, U.S.A.)

 

Abstract

Instrumental observations suggest that Lake Tanganyika, the largest rift lake in East Africa, has become warmer, increasingly stratified and less productive over the past 90 years (refs 1,2). These trends have been attributed to anthropogenic climate change. However, it remains unclear whether the decrease in productivity is linked to the temperature rise^{3, 4}, and whether the twentieth-century trends are anomalous within the context of longer-term variability. Here, we use the TEX₈₆ temperature proxy, the weight per cent of biogenic silica and charcoal abundance from Lake Tanganyika sediment cores to reconstruct lake-surface temperature, productivity and regional wildfire frequency, respectively, for the past 1,500 years. We detect a negative correlation between lake-surface temperature and primary productivity, and our estimates of fire frequency, and hence humidity, preclude decreased nutrient input through runoff as a cause for observed periods of low productivity. We suggest that, throughout the past 1,500 years, rising lake-surface temperatures increased the stratification of the lake water column, preventing nutrient recharge from below and limiting primary productivity. Our records indicate that changes in the temperature of Lake Tanganyika in the past few decades exceed previous natural variability. We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery.

*Correspondence e-mail: Jessica_Tierney@brown.edu

Link:  http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo865.html

Identifying potential synergies and trade-offs for meeting food security and climate change objectives in sub-Saharan Africa

Proceedings of the National Academy of Sciences, published online before print May 7, 2010; doi: 10.1073/pnas.0912248107

Identifying potential synergies and trade-offs for meeting food security and climate change objectives in sub-Saharan Africa

Cheryl A. Palm et al.

Abstract

Potential interactions between food production and climate mitigation are explored for two situations in sub-Saharan Africa, where deforestation and land degradation overlap with hunger and poverty. Three agriculture intensification scenarios for supplying nitrogen to increase crop production (mineral fertilizer, herbaceous legume cover crops—green manures—and agroforestry—legume improved tree fallows) are compared to baseline food production, land requirements to meet basic caloric requirements, and greenhouse gas emissions. At low population densities and high land availability, food security and climate mitigation goals are met with all intensification scenarios, resulting in surplus crop area for reforestation. In contrast, for high population density and small farm sizes, attaining food security and reducing greenhouse gas emissions require mineral fertilizers to make land available for reforestation; green manure or improved tree fallows do not provide sufficient increases in yields to permit reforestation. Tree fallows sequester significant carbon on cropland, but green manures result in net carbon dioxide equivalent emissions because of nitrogen additions. Although these results are encouraging, agricultural intensification in sub-Saharan Africa with mineral fertilizers, green manures, or improved tree fallows will remain low without policies that address access, costs, and lack of incentives. Carbon financing for small-holder agriculture could increase the likelihood of success of Reducing Emissions from Deforestation and Forest Degradation in Developing Countries programs and climate change mitigation but also promote food security in the region.

*Correspondence e-mail: cpalm@ei.columbia.edu

Link:  http://www.pnas.org/content/early/2010/05/06/0912248107.abstract

Estimated 6.9 million lives lost in DRC conflict

When a Death Toll Rivals the Holocaust

by Laura Heaton, Democratic Republic of Congo, February 11, 2010

With an estimated death toll of six million, the Holocaust is widely viewed as the singularly most devastating period in modern history. The word holocaust, derived from the Greek words meaning “burnt whole,” is now used almost exclusively to describe the state-sponsored massacre of European Jews. In the aftermath, countries came together to create the United Nations and craft international treaties intended to build a more cohesive international community that would be better prepared to respond in the future to horrors like they had just witnessed in Nazi Germany.

Yet despite the increased interconnectedness of the world and the international provisions in place to respond to humanitarian crises, the conflict in eastern Congo rages on even today without an effective international response – surpassing the Holocaust in number of years and now, even in number of lives lost.

In 2007, the International Rescue Committee, or IRC, released the results of a pivotal study, which found that 5.4 million people had died in eastern Congo since 1998. They also found that the death toll was mounting at a rate of about 45,000 people per month. But those figures are now nearly three years old. In a New York Times op-ed this week, Nick Kristof’s calculation caught my attention: “That would leave the total today, after a dozen years, at 6.9 million.”

Think about that … 6.9 million. It’s hard to fathom.

The vast majority of people who have died in eastern Congo perished from non-violent causes such as malaria, malnutrition, and other preventable diseases – symptoms of a conflict that has left Congo destabilized, its people displaced, medical services hard to come by, and food scarce. The death toll also masks the fact that an untold number of women, children, and even men who survive have suffered brutal rapes that leave lifelong physical and emotional scars.

Of course, a defining feature of the Holocaust is that a government masterminded it. What’s happening in Congo today isn’t genocide, though the legacy of genocide in neighboring Rwanda certainly lingers in the eastern Congo. There are a variety of perpetrators, motivated by ethnic tensions, the desire to control resources, opportunistic attempts to benefit from the lack of order – all facilitated by the impunity that reigns.
Furthermore, counting deaths in Congo is inherently challenging – precisely because of the violence and lack of infrastructure – as demonstrated in a recently reignited dispute over the IRC’s 2007 findings. Congo expert Jason Stearns provides an overview and his own insights, coming down in support of IRC’s initial findings, which after reading about the debate, I’m inclined to do too. (Science magazine’s blog has the full back-and-forth between IRC and the researchers at Canada’s Simon Fraser University who disputed IRC’s study.)

But the bottom line is that the sheer number of people who have died in eastern Congo over the past 12 years is unacceptable. Absent a public outcry to compel world leaders to make ending the conflict a priority -– by fully utilizing the tools at their disposal and finding other ways to put the pressure on those who benefit from Congo’s instability –- expect to see the death toll make new, horrific records.

We can all take action, too. Next week presents a rare opportunity to reach out to your members of Congress face to face in their home districts, and tell them that you expect U.S. leaders to take firm action to end the trade in conflict minerals that is helping to fuel the violence in eastern Congo. Visit Raise HOPE for Congo for details and to sign up for Advocacy Days during the Presidents Day recess, February 15–19, 2010.

Photo credit: Radio Okapi

Link:  http://genocide.change.org/blog/view/when_a_death_toll_rivals_the_holocaust

Environmental Research Letters, 5 (January-March 2010) 014010; doi: 10.1088/1748-9326/5/1/014010

Robust negative impacts of climate change on African agriculture

Wolfram Schlenker¹ and David B Lobell<sup>2,*

1</sup> Department of Economics and School of International and Public Affairs, Columbia University, New York, NY 10027, USA

² Department of Environmental Earth System Science and Program on Food Security and the Environment, Stanford University, Stanford, CA 94305, USA


Received 1 May 2009; accepted 27 January 2010; published 10 February 2010.


Abstract

There is widespread interest in the impacts of climate change on agriculture in Sub-Saharan Africa (SSA), and on the most effective investments to assist adaptation to these changes, yet the scientific basis for estimating production risks and prioritizing investments has been quite limited. Here we show that by combining historical crop production and weather data into a panel analysis, a robust model of yield response to climate change emerges for several key African crops. By mid-century, the mean estimates of aggregate production changes in SSA under our preferred model specification are –22, –17, –17, –18, and –8% for maize, sorghum, millet, groundnut, and cassava, respectively. In all cases except cassava, there is a 95% probability that damages exceed 7%, and a 5% probability that they exceed 27%. Moreover, countries with the highest average yields have the largest projected yield losses, suggesting that well-fertilized modern seed varieties are more susceptible to heat related losses.

*e-mail: dlobell@stanford.edu

Full open-access paper at this link:  http://www.iop.org/EJ/article/1748-9326/5/1/014010/erl10_1_014010.html

J. Burney et al., PNAS, Solar-powered irrigation significantly improves diet and income in rural sub-Saharan Africa

Solar-powered irrigation significantly improves diet and income in rural sub-Saharan Africa

ScienceDaily, January 5, 2010 — Solar-powered drip irrigation systems significantly enhance household incomes and nutritional intake of villagers in arid sub-Saharan Africa, according to a new Stanford University study published in the Proceedings of the National Academy of Sciences (PNAS). The two-year study found that solar-powered pumps installed in remote villages in the West African nation of Benin were a cost-effective way of delivering much-needed irrigation water, particularly during the long dry season.

"Significant fractions of sub-Saharan Africa's population are considered food insecure," wrote lead author Jennifer Burney, a postdoctoral scholar with the Program on Food Security and the Environment and the Department of Environmental Earth System Science at Stanford. "Across the region, these food-insecure populations are predominantly rural, they frequently survive on less than $1 per person per day, and whereas most are engaged in agricultural production as their main livelihood, they still spend 50-80% of their income on food, and are often net consumers of food."

Burney and her co-authors noted that only 4% of cropland in sub-Saharan Africa is irrigated, and that most rural, food-insecure communities in the region rely on rain-fed agriculture, which, in places like Benin, is limited to a three- to six-month rainy season.

"On top of potential annual caloric shortages, households face two seasonal challenges: They must stretch their stores of staples to the next harvest (or purchase additional food, often at higher prices), and access to micronutrients via home production or purchase diminishes or disappears during the dry season," the authors wrote.

Promotion of irrigation among small landholders is therefore frequently cited as a strategy for poverty reduction, climate adaptation and promotion of food security, they said. And while the role of irrigation in poverty reduction has been studied extensively in Asia, relatively little has been written about the poverty and food security impacts in sub-Saharan Africa.

Benin demonstration sites

To address the lack of data, Burney and her colleagues monitored three 0.5-hectare (1.24-acre) solar-powered drip irrigation systems installed the Kalalé district of northern Benin. The systems, which use photovoltaic pumps to deliver groundwater, were financed and installed by the Solar Electric Light Fund (SELF), a nongovernmental organization.

"As with any water pump, solar-powered pumps save labor in rural off-grid areas where water hauling is traditionally done by hand by women and young girls," the authors said. "Though photovoltaic systems are often dismissed out-of-hand due to high up-front costs, they have long lifetimes, and in the medium-term, cost less than liquid-fuel-based pumping systems."

Solar-powered pumps also can be implemented in an easily maintained, battery-free configuration, they added, "thereby avoiding one of the major pitfalls of photovoltaic use in the developing world."

In November 2007, the research team began a close collaboration with local women's agricultural groups in two villages in rural Benin. In Village A, which draws surface water from a year-round stream, researchers worked with residents to install two identical solar-powered pumping systems. In Village B, which relies on groundwater irrigation, water was pumped from 25 meters (82 feet) below the surface. Each solar-powered pumping system was used by 30 to 35 women affiliated with an agricultural group. Each woman farmed her own 120-square meter (1,292-square foot) plot. The remaining plots were farmed collectively to fund group purchases and expenses.

The researchers also chose two control villages for comparison with Villages A and B. Women's agricultural groups in the control villages continued to irrigate by hand, allowing for comparison of the solar-powered drip irrigation systems to traditional methods. "Household surveys were conducted in both treatment and control villages upon installation (November 2007) and following one year of garden operation (November 2008), and included detailed questions concerning consumption and agricultural production, as well as other socioeconomic, health and general questions," the authors wrote.

Striking results

The results were striking. The three solar-powered irrigation systems supplied on average 1.9 metric tons of produce per month, including tomatoes, okra, peppers, eggplants, carrots and other greens, the authors found. Woman who used solar-powered irrigation became strong net producers in vegetables with extra income earned from sales -- significantly increasing their purchases of staples and protein during the dry season, and oil during the rainy season. During the first year of operation, the women farmers kept an average of 18 percent by weight -- 8.8 kilograms (19.4 pounds) per month -- of the produce grown with the solar-powered systems for home consumption and sold the rest in local markets.

"Garden products penetrated local markets significantly," the authors found. "Vegetable consumption increased during the rainy season (the time of greatest surplus for the women's group farmers) for the entire four-village sample of households."

Survey respondents also were asked about their ability to meet their household food needs. Seventeen percent of the project beneficiaries said they were "less likely to feel chronically food-insecure. In short, the photovoltaic drip irrigation systems had a remarkable effect on both year-round and seasonal food access," the authors said.

Nutrition and sustainability

In terms of nutrition, vegetable intake across all villages increased by about 150 grams per person per day during the rainy season. But in villages irrigated with solar-powered systems, the increase was 500 to 750 grams per person per day, which is equivalent to 3 to 5 servings of vegetables per day -- the same as the U.S. Department of Agriculture's Recommended Daily Allowance for vegetables -- and most of this change took place in the dry season.

The research team also concluded that, despite higher up-front costs, using solar power to pump water can be more economically sustainable in the long run than irrigation systems that run on liquid fuels, such as gasoline, diesel or kerosene. "When considering the energy requirements for expanded irrigation in rural Africa, photovoltaic drip irrigation systems have an additional advantage over liquid-fuel-based systems in that they provide emissions-free pumping power," they added.

"Overall, this study thus indicates that solar-powered drip irrigation can provide substantial economic, nutritional and environmental benefits," the authors said. "With the proper support, successful widespread adoption of photovoltaic drip irrigation systems could be an important source of poverty alleviation and food security in the marginal environments common to sub-Saharan Africa."

Other co-authors of the PNAS study are Rosamond Naylor, director of Stanford's Program on Food Security and the Environment and professor of environmental Earth system science; Lennart Woltering and Dov Paternak of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Niger; and Marshall Burke of the Department of Agricultural and Resource Economics, University of California-Berkeley.

The research was supported by an Environmental Venture Projects grant from the Woods Institute for the Environment at Stanford University. The results are published in the January 4, 2010, online edition of PNAS.

Link:  http://www.sciencedaily.com/releases/2010/01/100104151923.htm

A. G. Patt et al., PNAS, 2009, Estimating least-developed countries’ vulnerability to climate-related extreme events over the next 50 years

Proceedings of the National Academy of Sciences, published online before print January 5, 2010; doi: 10.1073/pnas.0910253107 

Estimating least-developed countries’ vulnerability to climate-related extreme events over the next 50 years

Edited by Stephen H. Schneider, Stanford University, Stanford, CA, and approved December 4, 2009 (received for review September 10, 2009)

Abstract

When will least developed countries be most vulnerable to climate change, given the influence of projected socio-economic development? The question is important, not least because current levels of international assistance to support adaptation lag more than an order of magnitude below what analysts estimate to be needed, and scaling up support could take many years. In this paper, we examine this question using an empirically derived model of human losses to climate-related extreme events, as an indicator of vulnerability and the need for adaptation assistance. We develop a set of 50-year scenarios for these losses in one country, Mozambique, using high-resolution climate projections, and then extend the results to a sample of 23 least-developed countries. Our approach takes into account both potential changes in countries’ exposure to climatic extreme events, and socio-economic development trends that influence countries’ own adaptive capacities. Our results suggest that the effects of socio-economic development trends may begin to offset rising climate exposure in the second quarter of the century, and that it is in the period between now and then that vulnerability will rise most quickly. This implies an urgency to the need for international assistance to finance adaptation.

Link to abstract:  http://www.pnas.org/content/early/2009/12/15/0910253107.abstract