| Land use and land cover change(LULCC)caused by human activities and natural factors have led to the global native biodiversity loss and the alteration of ecological processes,goods and services in the various wetland ecosystems,particularly floodplains.Assessing long-term spatial and temporal land use and land cover changes and their impacts on the ecosystem services and functions of the valley floodplains,providing recommendations for future development and sustainable ecosystem management has become a hotspot topic in this research area.This study assessed the spatial and temporal patterns of land use and land cover change for the past 26 years,identified driving forces of such changes and simulated changes in 2040 of the study area.It investigated how land use and land cover change impact ecosystem service values,analyzed the needs and capacities of different land use and land cover types to deliver ecosystem goods and services,and proposed interventions suitable for wetland management in the Kilombero valley floodplain.Kilombero valley floodplain is one of the largest freshwater inland floodplains in East Africa,located in the Morogoro region,southeastern Tanzania.It provides a wide range of important ecosystem services and is also a habitat that supports a variety of plant and animal species.Landsat images and GIS methodology were used for the study;using quantitative and qualitative methods,and socio-economic surveys such as semi-structured questionnaire interviews,key informant interviews,ecosystem services assessment workshops and focus group discussions were used.The questionnaire was randomly and purposefully sampled in six selected villages in Kilombero,Ulanga and Malinyi districts.The sample included 369 households,and 15 people were involved in key informant interviews and focus group discussions.Also,ENVI 5.3 remote sensing software;the Landsat Thematic Mapper(TM)1990,Landsat Thematic Mapper(TM)2010 and Operational Land Imager(OLI)2016 provided free of charge in the archives of the United States Geological Survey(USGS)were used to analyzed and mapped the land use and land cover changes by Arc GIS 10.2 software.Based on the CA-Markov model integrated into the Terr Set software 2020 land use and land cover change in 2040 were simulated.The results show that:1.During the past 26 years from 1990 to 2016,the LULC changes in the study area are obvious.The forest in the study area is the largest part of the LULC type that decreased from19,544 km~2in 1990(64 percent)to 16,415 km~2(53.9 percent)in 2016.Bushland is the second-largest land cover type accounting for 18 percent of the total KVFP area in 1990 and8.1per cent in 2016,implying a 10 percent decreased change.Wetland area declined from 1415km~2 in 1990 to 261 km~2 in 2016,meaning the percentage decreased from 4.6 percent to 0.9percent that implied a decrease of 3.8 percent.In the same period,agricultural land and grassland increased by 11.3 percent and 13.3 percent,respectively.The simulation results of land use and land cover change from 2016 to 2040 based on the CA-Markov model indicate the proportion of wetland,bushland,agriculture,and grassland will increase by 135.6 percent,43 percent,35.3percent,and 9 percent,respectively,while the forest and water area will be further reduced by22.6 percent and 19.3 percent,respectively in the study area.The model also shows that the future increase in agricultural area and grassland would occur along the core low-lying flat ground of the Kilombero valley floodplain.2.These changes are driven by the intensification of human activities,particularly agriculture expansion,free grazing,timber extraction,charcoal production and settlement expansion.Furthermore,government policies,increased market demand,the prices of crops and wood products together with improved infrastructure,human population growth,agro-technology advancement,soil properties,topographic features and climate variability are major drivers of land use changes in the KVFP.These results on the drivers of the LULC change are consistent with the public survey.3.The ecosystem services value(ESV)estimates show,between 1990 and 2016,the total amount of ESV obtained using the modified local value factor method decreased by US$811.5million(26.6 percent).while estimated loss using the global value factor approach was US$3000.7 million(42.3 percent).The main reason for the decline in the total ESV is the decrease in the ESV of forest,wetland,bushland and water area,consistency with varied proportions during the study period.The decrease in the values of these ecosystem services is due to changes in LULC,mostly reduced area of the forests,bushlands,wetlands and water in the study area.Also,the study shows the contributions of the individual ecosystem services to the total ESV in the study area,food production and biological control increased over the period1990-2016,while other types of ecosystem services such as water regulation,climate regulation,erosion control,nutrient cycling,habitat/refugia and water supply values decreased significantly.The increase in the value of food production is mainly due to the increase in agricultural land.Moreover,the ecosystem service trade-off degree shown synergy is the common relationship among ecosystem services in the Kilombero valley floodplain for 1990-2016;thus synergy mostly occurred in all ecosystem services except for food production,biological control,pollination;and water regulation and soil formation.The trade-off degree between water regulation and soil formation is the lowest,and the synergistic degree between water regulation and disturbance regulation is the highest.Consequently,the relationship between water regulation and soil formation is the most serious among all ecosystem functions in the Kilombero valley floodplain.4.Kilombero valley floodplain has experienced a spatially decrease in the supply of ecosystem services.This is due to a decrease in the forest,bushland and wetland by 10.3%,10%and 3.8%,respectively that in the past 26 years.The changes in these natural ecosystems(forest,bushland and wetland)have greatly affected changes in the capacity to supply ecosystem services in the KVFP.The spatial-explicitly maps show that demands for ecosystem services have been spatially increased toward the core of the low-lying ground of the Kilombero valley for the period between 1990 and 2016.This is due to increased agricultural and urban areas by 11.3%and 0.1%,respectively.The urban area in this floodplain is characterized by low-density settlements blended with farmland concentrated along the major roads.The areas with a balance between ES supply and demand are mainly distributed in bare soil,grassland,and surrounding areas.Moreover,the average supply-demand budget index decreased from 1.8 in 1990 to 1.6 in 2016 for the last 26years.The supply-demand indexes show supply for the ecosystem services within KVFP exceeds the demand,with few exceptions of the pollination,crop production and fresh water supply,which show demand exceeds supply(High deficit).The high deficit areas of ES budgets are along with the agricultural land and urban area while high surplus areas were mostly concentrated in the ecological areas with low intensity of human activities and high natural land cover mainly forest,bushland and wetland.The high deficit area seems to increase towards the core of the low-lying Kilombero valley,indicating there is a greater impact of agricultural expansion and intensification on ecosystem services supply and demand for the past 26 years.Based on these research findings,this is study is considered helpful in providing baseline information on the relationship between land use and land cover change and ecosystem services values,supply and demand within the Kilombero valley floodplain.Therefore,this study recommends more efforts should be taken to reduce deforestation by reinforcing afforestation and reforestation programs,invest in efficient irrigation farming,facilitate wetland restoration programs and diversify livelihood activities to reduce the dependence on wetland resources to maintain the integrity of natural ecosystems of the Kilombero valley floodplain. |
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