A Concerted Effort to Save Tana

Transcription

1 A Concerted Effort to Save Tana GLOBAL COALITION FOR LAKE TANA RESTORATION Prepared by: Dr. Solomon Kibret Chair, Global Coalition for Lake Tana Restoration University of California, Irvine United States November

2 Acknowledgement This project was partly financially supported by Gojjam Global Alliance of Canada and Gojjam Global Alliance US. A number of people and institutions participated in this work. Drs. Abeyou Wale and Yihun Dile, members of the Scientific Committee of the Global Collision for Lake Tana Restoration, analyzed satellite images. Members of the Geospatial Center of Bahirdar University, namely Zinabu Getahun, Minyichil Alemu and Meleket Yibabie, helped in the data collection in the field. Members of the Amhara Regional Environmental Bureau such as Dr Belayneh Ayele, Mezgebu Asres, and Negash Atinafu participated in drafting the strategic roadmap. 2

3 Background Lake Tana is the largest lake in Ethiopia, accounting 50% of the country s freshwater resources. It is approximately 84 km long and 66 km wide, with a maximum depth of 14 m and a surface elevation of 1,788 m above sea level. Its surface area ranges from 3,000 to 3,500 km² depending on season. The lake is fed by several rivers, with 97% of the water coming from four major rivers: Gilgel Abay, Ribb, Gumara and Megech. The annual inflow to the lake is estimated to be 4,986 Mm 3 per year. The plains surrounding the lake (i.e. the Dembiya, Fogera and Kunzila plains in the north, east and southwest, respectively) form extensive wetlands favorable for large- and small-scale agriculture. As a result of the high heterogeneity in habitats, the lake and surrounding riparian areas support high biodiversity and are listed in the top 250 lake regions of global importance for biodiversity. Lake Tana hosts 65 fish species a quarter of which are endemic to the lake. Among them, it is home for eighteen species of barbus fish (i.e. of the Cyprinidae family) and the only extended cyprinid species flock in Africa. Other common fish species include tilapia (Oreochronmis niloticus) and catfish (Clarias gariepinus). A study in 1996 identified 217 bird species around the lake, with a minimum of 20, 000 water birds. The lake shore is also characterized by its extensive papyrus (Cyprus papyrus). Over 4 million people are estimated to live in the lake catchment and at least people are believed to live on the 37 islands in the lake The lake has tremendous socioeconomic benefits to the country. The major economic benefits include irrigation, hydropower generation, tourism and fishery. Several monasteries located in the lake s islands have historical and religious assets. Studies show that the lake basin has an irrigation potential of 517,500 hectares of land. The potential fish production of Lake Tana is estimated to be tons per annum. However, its current production is only about 1000 tons per year. Recent studies indicated a serious decline in fish stocks due to the spread of water hyacinth around fish spawning grounds. 3

4 Current threats of Lake Tana Water hyacinth, Eichhornia crassipes Martius (Pontederiaceae) is an exotic free-floating perennial plant that is native to South America. It is one of the fastest growing plants known. Water hyacinth is considered as an invasive species. If not controlled, it will rapidly and thoroughly cover entire surfaces of lakes and ponds dramatically impacting water flow, blocking sunlight to native submerged plants, and depleting the oxygen in the water - often choking aquatic animals such as fish. Major economic impacts caused by invasion of water hyacinth include interference with navigation, irrigation and power generation, and fishery. Water hyacinth is an aggressive invader and can form thick mats. Dense mats of this plant can also provide ideal mosquito breeding habitats. It is very important to control water hyacinth before the entire water surface is covered. Recent data have clearly showed that Lake Tana is critically infested with this weed and the aquatic biodiversity of the lake is extremely at risk. In 2011, water hyacinth was officially recognized as one of the top ten ecologically dangerous and worst invasive weeds infesting Lake Tana. Unpublished literature indicated that about 20,000 hectares of the north-eastern shore of the lake was estimated to be infested with water hyacinth. Likewise, a team of researchers from Bahir Dar University reported that about onethird of the shoreline (128 km length) of the lake was invaded by water hyacinth in According to gray the literature, the estimated coverage of the weed doubled in just two years. As a consequence, the lake has lost 75% of its fish production in recent years. This clearly shows the pressing threats of the weed on the lake s environment and aquatic life. Currently Lake Tana has faced serious ecological threats that affected its aquatic biodiversity. Pollution, sedimentation and water hyacinth infestation are the major threats to the lake. In October 2017, Global Coalition sent technical personnel to the area to study the current status of water hyacinth and identify control measures to eliminate the weed and restore a healthy ecosystem. A five-year strategic roadmap was also drafted together with the Regional Environmental Bureau. 4

5 Findings from the Global Collation for Lake Tana A team of researchers from the Global Coalition for Lake Tana Restoration (a US-registered notfor-profit initiative) and Geospatial Center of Bahirdar University spent a number of days in September-October 2017 around Lake Tana assessing the extent of water hyacinth coverage and assessing economic and ecological impacts of the weed on the environment. Using handheld GPS, the distribution of water hyacinth was determined. The results of the study indicated that a total of 5,037 hectares of the shoreline were infested by water hyacinth as of October The infested area covers the northern, northeastern and eastern shores of the Lake that stretches 140 km (Fig 1). Fig 1. Current distribution of water hyacinth in the northern, northeastern and eastern shorelines of Lake Tana, October

6 A total of 20 kebeles have been infested with water hyacinth in the northern, northeastern and eastern parts of Lake Tana (Table 1). These parts of the lake are known for agriculture and fishery. A number of rivers enter the Lake Tana in these sections of the lake. Consequently, large loads of sediment and dissolved nutrient washed away from upstream Tana catchment enter the lake through these rivers. Due to the presence of high dissolved nutrient such as nitrogen and phosphorus, river mouths have become favorable habitats for water hyacinths. The irony is that river mouths are important breeding grounds for fish, where the weed will impede its very existence. The presence of massive mats of water hyacinths will block sunlight and oxygen to the aquatic habitat which will significantly affect the fish population. A recent study indicated that the fish population in the Lake Tana basin decreased by up to 75% in the recent years. Perhaps, the emergency of the weed contributed to this remarkable fish stock decline. Table 1. Coverage of water hyacinth by kebele around Lake Tana, Oct No Zone Woreda Kebele Weed Status* coverage in ha 1 South Dera Mitsili 260 High Gondar Fogera Wagetera 155 Intermediate Nabega 326 High Libo Kemkem Tezamba 540 High Kab 348 High Agid 132 Intermediate Kirigna 18 Low 2 North Gondar Gondar Zuria Mitriha Aba Warka 195 Intermediate Firka Dangure Intermediate Sheha Gomene 33.5 Low Lemba 398 High Jarjar 339 High East Dembia Tana Woina 903 High Adisge Dinge 187 Intermediate Achera 756 High Seraba Dablo 591 High West Dembia Dahna Wawa 18 Low Gorgora 13.2 Low Abrjeha 14.6 Low Mange 15.2 Low Grand total 5,037 * Status is defined as follows: >200 ha High; ha intermediate; <100 ha low 6

7 Moreover, studies show that water bodies covered with water hyacinth are subjected to about eight times higher water loss than an open water. This resulted in more evaporation in the wetland where the weed exists. Perhaps, the drying of the wetlands of Dera and Fogera woredas may be related to the presence of this weed. Our findings have indicated that tens of thousands of households have lost their livelihood because of the invasion of water hyacinth. Unless appropriate measure is taken the impact will get worse on the local livelihood, national economy and aquatic ecosystem around Lake Tana. Among the 20 kebeles that are infested by water hyacinths, just four of them (Tana Woina, Achera, Seramba and Tezamba) accounted for 55% of the total weed coverage around the lake (Table 2). Generally, nine kebeles are considered as highly infested (>200 ha/kebele) and five kebeles are infested at intermediate level ( ha/kebele) whereas six kebeles are infested at low level (<100 ha/kebele) (Fig 2). Satellite images indicated that the weed were expanding at a rate of 13 ha per day during the rainy season (June- September) (Fig 3), mainly due to poor planning and management of manual campaigns. During these campaigns, people were not trained about weed removal procedures and designated sites were not arranged for disposal of the harvested weed. Most of the harvested weeds were left at the edge of the shoreline subjected to be washed away by rain which then dispersed the weed to a wide area as the weed also propagates vegitatively through its detached stolon. Fig 2. Relative density of water hyacinth across Lake Tana, Oct

8 Our study revealed the tremendous impact of water hyacinth on the functions of the Lake and a well-designed weed management approach is required to stop the weed from covering the entire lake. Satellite images showed that water hyacinth infested areas are very shallow and this understanding is important in selecting appropriate water harvesting machines based on local context. Based on the findings of this study, experts from the Regional Environment Bureau, Global Coalition and Bahirdar University drafted a five-year action plans that need to be done in order to eliminate the weed and restore a healthy ecosystem. Fig 3. Periodic increase of the water hyacinth mat around Lake Tana, based on high resolution satellite images (Note the difference in coverage between satellite data) (Wale et al, GCLR Scientific team) Fig 4. Water depth of areas infested with water hyacinth generated from satellite images (note shallow areas of the lake are currently affected by the weed) (Wale et al, GCLR Scientific team) 8

9 What need to be done? The Amhara National Regional State Regional Environmental Bureau in collaboration with Global Coalition and Bahirdar University has drafted a five-year strategic document that maps a detailed plan of actions needed to eliminate the weed and rehabilitate the degraded environment of the lake s catchment. The strategies identified short-term and long-term action plans. A total of 3 million USD is required to implement all activities planned for the next five years. Short-term plan The short-term plan aims creating a strong capacity at regional and local level and implement water hyacinth elimination activities across Lake Tana within the next one to one-and-half years. The cost for short-term activities is USD 700,000. a) Capacity building: In the short-term, a special Unit called Water hyacinth control and management Unit will be structured at the Regional Environmental Bureau. This Unit will lead and coordinate all activities around Lake Tana. This Unit will support and work closely with local NGOs and other stakeholders to achieve the anticipated goals of the strategic document. Highly trained professionals (including experts of aquatic plant, environment, GIS and M&E) will be hired. The Unit will also have kebele coordinators in each of the 20 infested kebeles. Kebele coordinators will be trained locally and ensure the implementation of action plans at local scale. In addition, international trainers with a great deal of experience in water hyacinth control in Africa and elsewhere in the world will be engaged to train experts at governmental and non-governmental agencies who are working to address Lake Tana s challenges. b) Water harvesting machines: three water hyacinth harvesting machines are needed to work in northern, northeastern and eastern parts of the lake. Daily operational, maintenance and manpower costs are calculated. Conveying belts that extend from the water body to the dry land are also required to unload the harvested water hyacinth 9

10 from the machines and transport it to the shoreline. Carts and trucks will then transport the harvested weed from the shoreline to the designated disposal area (large pits) prepared away from the water body. The weed currently existing in twelve highly infested kebeles (of the total 18) will be removed using these machines. c) Manual removal: For health and practicality reasons, manual weed removal are confined to only a few kebeles which are with low risk of schistosomiasis and practically possible. d) Grass plantations: Local studies indicated that endegenous grass species help avoid water hyacinth expansion due to their ability to absorb excessive nutrients from the water. In areas where water hyacinth is removed, such grasses will be planted and maintained in order to create conditions unfavorable for the weed. e) Waste water management system: A well-studied waste water management system will be implemented around Lake Tana in order to reduce dangerous waste water influent into the lake catchment. f) Operational researches: Areas of knowledge gap will be identified by the Scientific Committee and researches will be conducted to understand the mechanism of water hyacinth propagation and distribution. Environmental variables that contribute to favorable conditions for water hyacinth development will also need to be assessed well. The effect of control measures will also be periodically assessed and approaches will be revised accordingly. Biological control measures are still in study phase and this needs to continue until we understand their impact on the environment. Long-term i) Environmental rehabilitation: The environment of Lake Tana has deteriorated due to high rates of deforestation and increased agricultural practices. Afforestation programs are needed to restore the forests of the catchment. Planting endegenous plants and protecting deforestation is critical to rehabilitate the degraded environment and reduce soil and nutrient erosions upstream of the lake. 10

11 ii) Ecosystem payment: Regulations will be drafted to charge ecosystem payments from beneficiaries operating businesses around Lake Tana. This helps to generate income for environmental management activities. Such incomes help reinforce wastewater and environmental management activities around the lake s catchment. Businesses will be trained to be environmentally friendly. iii) Improving fish productions: New policies and regulations are needed to protect illegal fishery and maintain a healthy fish habitats. Periodical trainings and discussions will be conducted with the fishery community to help them contribute in maintaining a healthy aquatic environment. iv) Improving agricultural practices and livestock management: Improved agricultural practices are required to reduce soil erosions. New technologies and agricultural practices that fit the area traditional and cultural assets will be implemented and such practices will help manage the environment better. Improved livestock management will be practiced to avoid overgrazing which facilitates soil erosion. Monitoring and evaluation Monthly, quarterly and annual field and satellite data will be collected and analyzed by an M&E Team composed of experts from the Global Coalition, Bahirdar University and international universities. Time-series satellite images will be analyzed to monitor the status of water hyacinth and environmental factors around Lake Tana. These reports will be discussed with the Regional and Federal Environment Bureaus in Ethiopia. In addition, the reports will be publicly available on the Global Coalition website for anyone interested to follow-up the work. Global Coalition will host symposiums annually to discuss M&E findings with Chapters formed in each state and country across US, Canada, Europe and Australia. The Board of Trustees of the Global Coalition will oversee overall activities of the Coalition and partners working to address the current challenges of Lake Tana. The Coalition aims to be open, transparent and participatory in decision-making and directions it takes while managing and providing technical, material and financial supports to the work done around Lake Tana. 11

12 Picture: Water hyacinth mat in Achera, Dembia Woreda, Ethiopia (Oct 25, 2017) 12