Densely populated rural areas in the East African Highlands have faced significant intensification challenges under extreme population pressure on their land and ecosystems. Sustainable agricultural intensification, in the context of increasing cropping intensities, is a prerequisite for deliberate land management strategies that deliver multiple ecosystem goods (food, energy, income sources, etc.) and services (especially improving soil conditions) on the same land, as well as system resilience, if adopted at scale. Tree based ecosystem approaches (TBEAs) are among such multi-functional land management strategies. Knowledge on the multi-functionality of TBEAs and on their scaling up, however, remains severely limited due to several methodological challenges. This study aims at offering an analytical perspective to view multi-functional TBEAs as an integral part of sustainable agricultural intensification. The study proposes a conceptual framework to guide the analysis of socio-economic data and applies it to cross-site analysis of TBEAs in extremely densely populated Rwanda. Heterogeneous TBEAs were identified across Rwanda's different agro-ecological zones to meet locally-specific smallholders' needs for a set of ecosystem goods and services on the same land. The sustained adoption of TBEAs would be guaranteed if farmers subjectively recognize their compatibility and synergy with sustainable intensification of existing farming systems, supported by favorable institutional conditions.
Multifunctional soil conservation strategies have the capacity to control soil erosion as well as increase its quality, thus leading to sustained yields as long as planners have knowledge on the severity of soil loss. A comprehensive methodology that integrates Revised Universal Soil Loss Equation (RUSLE) model and Geographic Information System (GIS) techniques was adopted to determine the soil erosion vulnerability within Katabuvuga, Nyamyumba and Mukamira watersheds in western part of Rwanda, with the aim of supporting planning of land and water management interventions. The dominant slop class in all watershed was 16-40% covering 50% in Katabuvuga watershed, 43% in Mukamira watershed and 70.6% in Nyamyumba watershed. High erosion risk was recorded in Mukamira (72 %) and it was followed by Nyamyumba (46 %). The average soil loss in selected watersheds was 32t/ha/year. Among the various studied watershed, highest average loss was reported in Nyamyumba watershed (37t/ha/year) while the lowest average was in Mukamira watershed (28t/ha/year). Soil loss was higher in cropland and lower in settlement. The average loss of nutrients was 1705 kg/ha/year of carbon, 155 kg/ha/year of nitrogen, 3 kg/ha/year of phosphurus and 111 kg/ha/year of potassium, the highest nutrient loss occurred in cropland. Based on the cost of NPK the average value of N lost per ha per year is 167507 Rwandan Francs (Rwf) while the value of P and K loss per ha per year is 3309 Rwf and 120189 Rwf respectively.
This study determined the change and distribution of land-uses/covers along the landscape, and evaluated the nutrient status of the top soil layer in the Lake Kivu Pilot Learning Site (LKPLS) benchmarked micro-catchments. Soil physical and chemical properties were quantified using triplicate soil samples collected from each land-use/cover at two depths (0-15 and 15-30 cm) in three LK PLS Learning Innovation Platform (IP) sites (Bufundi in Uganda, Mupfuni-Shanga in D.R. Congo, Gataraga in Rwanda). Small scale agriculture has increased in all the benchmarked micro-catchments at the expense of other land-uses/covers. In the settlement areas land-use/cover distribution along the landscape varied across sites and countries; the major one being eucalyptus woodlots, wetland, and perennials and annuals crops in Bufundi; annuals and perennials crops in Mupfuni-Shanga; and annuals crops in Gataraga. Perennial crops tended to occur at the footslope and valley bottoms, while the annuals occurred at the upper backslopes and summits. Available P and K were relatively higher and C/N ratio (7.28) was the lowest in Mupfuni Shanga. Annual crops had the lowest available P and N across site ( < 0.05). The key nutrients N, P and K were below the critical values for plant growth for Bufundi.
Rwanda, a small but rapidly developing central African nation, has undertaken development of natural capital accounts to better inform its economic development through the World Bank's Wealth Accounting and Valuation of Ecosystem Services (WAVES) Partnership. In this paper, we develop ecosystem service (ES) models to quantify ecosystem condition and physical supply components of ecosystem accounts in Rwanda from 1990 to 2015. We applied the InVEST carbon storage, sediment delivery ratio, nutrient delivery ratio, and annual and seasonal water yield models to map changes in potential ES supply nationwide. We also quantified flows of sediment, water and nutrients to 96 hydroelectric dam, irrigation dam and water treatment plant sites. Over a 25‐year period, we found declines in all ES, which were most strongly driven by conversion of forests to cropland. Declines were most pronounced from 1990 to 2000 and 2010 to 2015; ES were relatively stable from 2000 to 2010 (with the exception of nutrient exports to water bodies, which jumped most sharply from 2000 to 2010). From 2010 to 2015, over 42% of Rwanda's water‐use sites (representing 9% of the nation's hydroelectric generation capacity and 59% of its water treatment capacity) had upstream increases in sediment export and quick flow greater than the national average. Half of Rwanda's water treatment plants had upstream phosphorus exports greater than the national average. Our results quantify nation‐wide ES trends, their implications for key water‐dependent industries, and the importance of protected areas in safeguarding ES flows and potential supply in Rwanda. They also provide data that can be integrated with existing land, water and economic accounts for Rwanda, as well as a baseline to inform development strategies that better link economic and environmental goals. A free Plain Language Summary can be found within the Supporting Information of this article.
Experiences in smallholder contexts indicate frequent mismatches between technologies introduced and needs of farmers who must make complex decisions in reallocating their limited resources under highly risky ecological and market contexts. This study proposes a cost-and time-effective, easy-to-implement approach to identify farmers' priorities and critical intervention areas, and presents its application in guiding an agroforestry strategy in Rwanda. It was found that different tree species have distinctive enabling vs. constraining conditions under different agroecological contexts in the perspective of smallholder farmers. Tree species preferred by farmers were not necessarily widely adopted if multitudes of conditions were not enabling. The essential conditions for sustainable adoption include: quality materials/inputs are available; technologies are compatible with existing local farming systems; they are resilient to climate risks/resistant to pests-diseases; management is not complicated; and, there is guaranteed access to markets. The results show that there will not be a silver bullet national strategy to scale up agroforestry. Instead a matrix kind of strategies-to promote enabling conditions and address constraining conditions for priority species in specific agroecologies-will be required. The proposed concept should be further refined for wider agricultural technology transfer debates to break the myths of low uptakes by smallholders.
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