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Godorya Mangrove ViabilityTree Mortality in the Foret de Day
Republic of Djibouti22-28 October 2017
The US Forest Service in support of the US Department of Defense and US Embassy in Djibouti
Thomas E. DeMeo, PhDRegional EcologistUSDA Forest ServicePortland, OR [email protected]
Benjamin L. Branoff, M.Sc.Department of BiologyUniversity of Puerto Rico-Rio PiedrasSan Juan, PR [email protected]
Program contact: Natasha MarwahUS Forest ServiceInternational ProgramsAfrica and Middle East [email protected]
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ContentsExecutive Summary............................................................................................................................................3
Acknowledgements.............................................................................................................................................4
Introduction........................................................................................................................................................4
About the US Forest Service...........................................................................................................................5
Visit Objectives................................................................................................................................................5
Godorya Mangrove Assessment.........................................................................................................................5
Assessment Methods......................................................................................................................................6
Social Context..................................................................................................................................................7
Results..............................................................................................................................................................8
Windbreak Fence and Tree Planting Site....................................................................................................10
Recommendations........................................................................................................................................11
Mitigate Sand Deposition..........................................................................................................................11
Strategic Tree Planting.............................................................................................................................11
Consider Water Shortages when Planning Environmental Sites...........................................................12
Foret de Day......................................................................................................................................................12
Assessment Methods....................................................................................................................................13
Social Context................................................................................................................................................13
Results............................................................................................................................................................14
Recommendations........................................................................................................................................14
Manage Water Use in the Upper Watershed...........................................................................................14
Livestock Management.............................................................................................................................15
Long-Term Ecosystem Assessment.........................................................................................................15
Conclusion.........................................................................................................................................................15
References.........................................................................................................................................................16
Appendix 1.........................................................................................................................................................16
Appendix 2.........................................................................................................................................................17
Appendix 3.........................................................................................................................................................17
Appendix 4.........................................................................................................................................................18
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Executive SummaryThe Horn of Africa faces a number of environmental challenges including prolonged drought and an increasingly dry climatic trend. In October, 2017 a US Forest Service (USFS) team traveled to Djibouti to visit two specific sites that have been affected by these climatic changes: the Godorya mangroves on the north coast and the Foret de Day reserve at high elevation (1,450 meters) also in the northern part of the country.
The Godorya mangroves, encompassing 240 hectares, appeared viable overall with two main concerns. Some areas show signs of dieback and degradation from khamsin winds (hot, sand-laden winds) depositing and smothering the plants with sand and silt, a form of a desertification process. In other areas, the mortality is more subtle, occurring only in discreet spots and for no readily apparent reason. The USFS team investigated possible reasons for this decline and collected soil samples for subsequent contaminant analysis. One theory is that the mortality is occurring in areas receiving less fresh water in the system from rainfall and runoff at higher ground than in previous years. The long-term drying trend in the region and local anecdotal information about decreased rainfall supports this hypothesis.
The Government of Djibouti is deploying efforts to stop the mangrove desertification by building windbreaks made of wooden posts and planting trees. These efforts can be refined by carefully selecting and vetting tree species best adapted to the site without becoming invasive. Planting trees and other native vegetation should be done on nearby clay soils adjacent to the sand dunes, when possible, rather than on the dunes in sandy soils.
In areas when mangroves have died in discreet spots, dead trees can be cleared and mangrove seedlings planted. However, site managers should leave some wood on the ground in order to protect seedlings and avoid shifts in sediment. The long term outlook for Godorya, however, will most likely be shaped by an inevitable drying climatic trend to which the environment must adapt.
Foret de Day featured a very different environment—a cloud forest at 1,450 meters in the Goda Mountains. The Foret de Day reserve is well known in Djibouti as a recreation area to enjoy cooler temperatures and attractive mountain scenery. Foret de Day is a Juniperus forest with a Combretum understory. Unfortunately, in recent years, nearly all of the Juniperus overstory has died, resulting in a forest with a skeletal appearance. Herbicides may have been used on the forest in the early 1990s and the USFS team collected soil samples for subsequent analysis. The team found no evidence of insect or disease mortality. The most likely reason for juniper dieback is a lack of water. The Forest de Day ecosystem likely developed with a unique set of moisture inputs from fog drip and drainage into the forest from higher elevation areas, coupled with elevation and temperature regimes.
With a drying climate in the region, water coming from fog is likely declining. Additionally, agricultural development at higher elevation areas is likely restraining the amount of water flowing into the area. The forest reserve is also grazed, removing a vegetation layer that can help retain moisture. USFS recommends seeking ways to store and retain more water on the reserve. Perhaps
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agricultural practices outside the reserve could be adjusted to use less water. To address grazing, reserve managers should test grazing pressure and response by fencing a small frequently grazed area (20 meters x 20 meters) and testing the response of the rested site over two to three years. Based on this information, livestock grazing pressure can be adjusted accordingly. Overall, however, management of Foret de Day will need to reflect the inevitable long-term regional drying trend.
AcknowledgementsThe USFS team gratefully acknowledges the contributions of all who contributed to a very interesting and successful trip. Colonel Jacob Abrami, Army attache at the US Embassy, and Natasha Marwah of the US Forest Service International Programs office, were instrumental in forming the purpose and objectives of our mission. Major Chris Hettinger, Bilateral Affairs Officer, along with Merry Walker and Abdi Mohammed Abdi of the Embassy’s Economic and Commercial Section, set up our logistics for the trip. Chris and Merry accompanied us throughout the trip and made sure everything ran smoothly. They were also a wealth of information on the local context and helped us adjust quickly.
USFS also recognizes Beydane Chigi of the Programme d’appui à la Réduction de la Vulnérabilité dans les Zones de Pêches Côtières (PRAREV) who facilitated our work at the Godorya mangroves and ensured personnel were available to assist. The local fishermen’s association, let by Ibrahim Oudoum ([email protected]) was also a key part of the visit and we were humbled by their local knowledge and remarkable hospitality. Finally, we thank all the drivers who got us to and from our destinations safely.
IntroductionThe Republic of Djibouti occupies a strategic geographic location at the intersection of the Red Sea and the Gulf of Aden, serving as an important international shipping portal and refueling center for East Africa, Europe, the Middle East and Asia. Djibouti also hosts a large US military base at Camp Lemonnier, critical for regional security and stability. While predominantly arid and semi-arid, the country also boasts pockets of unique ecosystems including mangroves, evergreen forests, rare giant juniper trees, and wild olive groves that serve as important habitat for wildlife. Unique aquatic ecosystems, the rare, endemic Djibouti francolin, and its location along the Rift Valley and Red Sea flyway are just a few of the reasons that Djibouti is listed as an international wildlife and biodiversity hot spot and has become the focus of recent international conservation initiatives, particularly for migrating and soaring birds.
The country has a coastal zone as well as notable mountains, canyons, and a complex geology generated by the collision of the African and Arabian plates. It is also home to Lake Assal, the lowest point in Africa and saltiest lake on the continent. Djibouti also has distinctive vegetation, including two ecosystem types that were the focus of the USFS visit in October: mangroves and a high elevation cloud forest in the Goda Mountains.
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The USFS team’s visit was coordinated at the request of the US Department of Defense as part of a broader environmental security effort in Africa. In Djibouti, potential shortages of water, wood and arable land can potentially create social conflict. The Djiboutian government Ministère de l’Agriculture, de L’Eau, de la Pêche, de l’Elevage Chargé des Ressources Halieutiques (Ministry of Agriculture, Water, Fisheries, Livestock, and Saltwater Resources, known by the acronym MAEPE-RH) was also interested in a technical review of its mangrove protection work in Godorya, on the north coast of the country (Badji 2016). The in-country team included Major Chris Hettinger, Bilateral Affairs Officer at the US Embassy; Merry Walker, Economic and Commercial Officer at the US Embassy; and Tom DeMeo and Ben Branoff with the US Forest Service.
About the US Forest ServiceThe US Forest Service (USFS) manages forests, grasslands and many diverse ecosystems around the United States. Through its International Programs office, USFS provides technical assistance and exchange opportunities in over 90 countries around the world through partnerships with governments, NGOs, and universities. USFS has worked in East Africa for over a decade on a variety of natural resource issues through the support of the US Agency for International Development.
Visit ObjectivesThe USFS team’s visit objectives were:
Assess the dieback of mangroves at Godorya and collect data to analyze reasons for this dieback;
Review current strategies for addressing the dieback and offer recommendations for improvement and enhancement;
Review the dieback of trees in the Foret de Day reserve; Collect soils data to analyze chemicals and other potential anthropogenic causes of the
dieback; Provide recommendations for enhancing land management at both sites.
Godorya Mangrove AssessmentInternationally, mangroves are recognized as one of the world’s most valuable ecosystems. They control wind and soil erosion, serve as nurseries for vital fish resources, can be used as flood barriers, and they filter out pollutants (Witsen 2012). Mangroves also sequester carbon, fixing 20% more carbon on average per unit area than other tropical forests (IUCN 2011).
The Godorya mangroves are on the northern coast of Djibouti. This site features 240 hectares of mangroves, the largest mangrove stand in the country. Loss of mangroves is of great concern-approximately 25 to 50 percent of the mangroves in Godorya have been lost. Stresses on the ecosystem include sand deposition from annual khamsin winds, apparent reduction in rainfall over the past 10 years, and a reduction in water input from inland areas through runoff. Khamsin (or “fifty” in Arabic) refers to an approximately 50-day period of strong winds in July and August each year. Winds can move sand and loose soil with considerable force and deposit them into dunes.
Within the MAEPE-RH, there is a program to support reducing vulnerability of coastal fisheries areas (Programme d’appui à la réduction de la vulnérabilité dans les zones de Pêches côtières, or
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PRAREV). PRAREV has been working to replant mangroves in areas that have been dying and also to halt areas of sand dune accumulation from khamsin winds. 2018 is expected to be the last year of the project.
Assessment MethodsA number of different factors can affect mangrove growth and viability. The USFS team investigated salinity levels with a refractometer, recorded tidal fluctuation with an automated data logger, collected soil samples, and made general ocular observations at the site.
Salinity levels, if too high, can damage mangroves. Ideal salinity for mangrove survival is 5 to 10 parts per thousand (ppt). Sea water levels (35 ppt) are acceptable, but levels near 100 ppt will cause mortality. USFS measured salinity using a refractometer to gauge the density of a small water sample through the refraction of light. Water with higher salinity will be denser and thus, have a greater light refraction angle. The team measured water at the surface, when present, and within the soil at a depth of 20 cm after extraction using a small tube and syringe. Tidal fluctuation helps move the water affecting mangroves. The daily movement can help keep salinity levels from becoming too high and deliver nutrients and oxygen to mangrove roots while removing waste. Reduced tidal fluctuation can cause a problem for mangrove viability. Tidal fluctuation was recorded with a device tied to an anchor and then retrieved the following day by PRAREV staff. The device measures depth by means of water pressure every 15 minutes, and thus provides a time series of the fluctuation in sea levels.
The USFS team also collected soil samples for subsequent lab analysis for sodium, total nitrogen, oil, and heavy metals (copper, zinc, and lead). Sodium levels will indicate salinity. Nitrogen is a metric of a key nutrient essential for plant growth. Oil will indicate whether there is any pollution from oil escaping from boats at the port. Heavy metals are commonly found in human sewage. None of these factors appeared to contribute strongly to mangrove dieback, but the team wanted to be thorough in its analysis.
General ocular observations included looking for soil deposition, evidence of changes in water levels or flow patterns, and extensive consultation time with the local community on the short- and long-term history of the area. Along with personnel from PRAREV and the local community, USFS sampled three sites. The first site had the most mangrove mortality and was along a channel where khamsin winds had deposited sand in dunes (Figure 2).
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Figure 1 Dunes deposited by khamsin winds have resulted in mangrove mortality at Godorya. Dead mangroves can be seen in the upper left of the photo.
The second site was an open plain that never had mangroves, according to community anecdotes. The site can serve as a comparison to the other sites. Avicennia roots were emerging from the soil in places, so it may become somewhat colonized over time.The third site was a small (perhaps 0.25 hectare) area of dead mangrove that had been cleared of dead wood by PRAREV and the local community and then planted with Rhizophora mangroves in February 2017.
At each site, the USFS team collected data at multiple sampling points. (See Appendices 1,3 & 4) At each sampling point, the team recorded location in latitude/longitude using a GPS unit, the distance from the channel (estimated by pacing), and a salinity measurement (where possible). The team also collected a soil sample a 5 cm depth and stored it for subsequent analysis in the US. Finally, the team also took a photo point of the specific sampling site and general photos of each site.
Social ContextThere is ample evidence worldwide of the critical importance of involving local communities in conservation efforts (GNF 2015, CBEMR 2017, Enright and Kampongsun 2017). In order to ensure recommendations are followed and meeting the needs of Djiboutian stakeholders, the USFS and US Embassy teams met PRAREV and local community leaders to hear about their objectives, activities, accomplishments, and aspirations. The meeting was in a small coastal settlement established on the beach near the mangroves. The settlement consists of roughly twenty individuals, although they would like to be able to increase their size to 50-100. Ibrahim Oudoum (head of the local fisherman’s association) reported that the community’s greatest need was for fresh water. However, digging a well in the area would be challenging because it would likely need to be at great depth and could generate brackish water and the community near the mangroves is very remote.
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Results Tidal fluctuation in the lagoon near the coastal settlement was strong (approximately 1.5 m over 24 hours) and thus, was not a problem affecting the mangroves. (See Figure 3). Salinity levels were 35 ppt in the lagoon and 40-45 ppt in soils (where a sample could be collected). 35 ppt is the normal level of salinity in sea water. 40-45 ppt in soils is acceptable for mangroves. When soil samples are analyzed in the lab in the US, further information will be gleaned and shared.
Figure 2 Water levels, relative to mean sea level (MSL), measured over the course of 24 hours in the main channel of Godorya mangroves. Depths indicate a healthy semi diurnal tidal cycle with a daily range of ~1.5m. This is sufficient to provide adequate water exchange within the mangroves.
Most likely, sand dune accumulation from khamsin deposition is killing mangroves at the first site. In other areas, mortality occurs in spots and the cause is more difficult to discern. Community members and local government officials noted that rainfall has been decreasing in this area over the past 10 years, and that this has coincided with mangrove mortality. Godorya is situated at an old river delta and it may be possible that the freshwater inputs draining into the mangroves are reduced or absent from their former state. Direct freshwater input from rainwater could have also decreased.
Weather data from Djibouti International Airport shows no changes in wind speed or direction since 2005 (Figure 4), suggesting sand deposition from khamsin winds should not have increased significantly. Instead, it is likely that prolonged drought years and reduced rainfall has caused aerosolized soils that are picked up by strong wind, a phenomenon associated with desertification.
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Figure 3 Weather data from Djibouti international airport shows no change in wind speed or direction from 2005 to 2017. The hamseen phenomenon occurs for roughly fifty days of the year, as indicated by a change in wind direction during that time.
Rapid dieback of the Godorya mangroves is evident in satellite based imagery depicting vegetation from years 2005 and 2017 (Figure 4). The Normalized Difference Vegetation Index (NDVI) data is acquired from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites and represents the density of vegetation in an area as inferred from light absorption by chlorophyll. The green and yellow colors represent the mangrove area in the black boundary; the difference in color in 2017 illustrates the dieback/change in mangrove density. Soil tests revealed no significant abnormalities.
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Figure 4 NDVI data from MODIS imagery in 2005 (left) and 2017 (middle) show a decrease in vegetation density within the Godorya mangrove system, which is indicated by the line. NDVI values of 0 and 1 correspond to no vegetation and full vegetation, respectively. The change is represented as a percent change from 2005 values (right). Most of the mangroves experienced no change or loss, although there are some areas of increased vegetation surrounding the mangroves.
NDVI data from Godorya show significant reductions in vegetation, not only in and around the mangrove system but also in surrounding terrestrial landscapes (Figure 5). This suggests the Godorya dieback is not limited to the mangroves and is probably caused by regional climactic changes.
Figure 5 Regional NDVI data from MODIS imagery in 2005 (left) and 2017 (middle) show an overall decrease in vegetation density in the region surrounding Godorya. NDVI values of 0 and 1 correspond to no vegetation and full vegetation, respectively. The change is represented as a percent change from 2005 values (right). While some areas have increased vegetation coverage, likely due to small crops, the overall trend for the region is a decrease.
Windbreak Fence and Tree Planting SiteThe USFS team visited a site 14 km from the fishing settlement at Godorya. This area had mangroves that had been badly affected by khamsin wind deposition of sand, which killed the mangroves. A fence made of mangrove wood brought 14 km from Godorya was put in place to intercept the sand deposition. This had some mitigating effect, but unfortunately, most of the trees planted (palms and Cupressus) in the sand dunes died (Figure 6).
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Figure 6. Tree seedling mortality at Godorya planting site.
Recommendations
Mitigate Sand DepositionThe most important and immediate action that should be taken to stop the loss of the Godorya mangroves is to prevent the effects of sand deposition from khamsin winds. Although the effects of the khamsin winds are not intensifying over time, this annual weather event will likely continue to have adverse effects on the Godorya mangroves if left unchecked due to climatic factors and loose sand deposits. Satellite imagery analysis (Figure 4) shows that the area is losing mangroves around the edges. Windbreaks through fencing should continue to be built and should be strategically placed in areas some distance from the mangrove. By the time the sands get to the mangroves, it may be too late.
Strategic Tree PlantingWindbreaks from trees should also be carefully considered and strategically placed. Planting trees directly on sand dunes is not advised, since it will take a considerable amount of water and organic matter in the soil in order for the trees to survive. Trees should instead be planted a certain distance away in the clay soils. Site managers should also use native species for planting, if possible. The palm species may work well, if it is a native species and planted on better soil. A coastal shrub may be a candidate for planting to hold soil (Figure 7). Another option for stabilizing soil may be the coastal shrub Abutilon mauritianum, native to East Africa (Dharani 2011). Casaurina equisitifolia, a non-native species already in Djibouti, may also be a good candidate based on ability to grow in harsh coastal conditions. However, Casaurina equisitifolia is also reported as invasive in a number of countries (World Agroforestry Centre 2002). Species should be carefully chosen, and species trials may be merited.
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Figure 7 Unidentified coastal shrub in the Godorya area that may hold promise for soil stabilization planting efforts.
Consider Water Shortages when Planning Environmental SitesThe spotty dieback observed among the mangrove stands is likely due to changes in freshwater availability to the mangrove system. Local community members reported that rain has declined over the past 10 years. Since the Godorya mangroves are situated on a delta-type system at the ocean, upstream freshwater inputs may have declined as well because of less rain and/or upstream use by the local communities.
One study on the climate of the Horn of Africa indicates global climate change as a likely cause for the recent overall decrease in rains in the region (Tierney et al. 2015). A long term drying trend during the long rains (March to May) is causing drought. Rainfall during the short rains (September to November) is expected to increase. This study presents strong evidence that the recent decrease in rainfall in the region is not a result of small cyclical variability, but is instead following trends in anthropogenic global climate change. This study also indicates that climate models for the Horn of Africa are probably flawed, as they do not match historical records, and thus any prediction of increased rainfall in the region is likely to be inaccurate. These findings suggest the recent drought is not going to improve. Any environmental planning and interventions should anticipate long-term water shortages in the future.
Mangrove Wood RemovalOne of the ongoing strategies to further alleviate sand deposition and lagoon filling was the removal of dead mangrove wood. We recommend that while some removal may be healthy and successful in preventing accretion, full removal is not advised. This is for two reasons. The first is the possibility of removing structural integrity in the mangrove soil, which may exacerbate mangrove diebacks. The other is the removal of mangrove carbon from possible sequestration. Such sequestration helps
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alleviate greenhouse gas accumulation in the atmosphere and is an important service of mangroves. Removing the wood allows it to be decomposed and creates more greenhouse gases.
Further, with wood that is removed, it may be possible to explore sustainable charcoal production. Charcoal is an important fuel source for many of the local communities, who otherwise harvest from surrounding shrublands, further exacerbating the ongoing desertification. Using the mangrove wood for charcoal may alleviate the pressure on surrounding shrublands by providing a sustainable alternative wood source. Such practices must be done sustainably, however, without compromising the mangrove forest.
Foret de DayThe Foret de Day Reserve is primarily a Juniperus/Combretum forest at 1470 meter elevation and is a popular recreation area for Djiboutians to enjoy cooler temperatures and a forest setting, uncommon in the rest of the country. The reserve is about 3.2 km2 with a larger forest surrounding the site. Near the forest, there is also a spectacular canyon with hiking trails and leopards. Unfortunately, nearly all of the Juniperus overstory in the forest has died over the past 10 years, giving the landscape a skeletal appearance (Figure 8). In contrast, most of the understory of Combretum and other species remains alive.
Figure 8 Dead Juniperus overstory at the Foret de Day reserve.
Foret de Day is grazed by livestock, including cattle and goats. It is a tourist destination with modest facilities including a hotel and a campement touristique in the local village outside the reserve. The President also has a home adjacent to the reserve and the military (Republican Guard) has a small base nearby. There are small farms in the upper watershed from the reserve, growing qaat (leafy narcotic) and subsistence food crops. The government attempted to replant Juniperus
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seedlings but the trees died at 1 meter height for unknown reasons, even though they had been consistently watered.
Assessment MethodsThe USFS team started their assessment near the old governor’s house, now in ruins. Starting just south of the house, the team ran a transect from north to south with sample points in different slope positions (Appendices 2,3 & 4). At each point, the team collected latitude and longitude, elevation, four photos, and one each facing the cardinal directions (north, east, south, and west). The team also collected soil samples to analyze for herbicides-there is a rumor that the area may have been sprayed with herbicides during the civil war from 1991-1993. To obtain measurements of spatial variation, the team also sampled soils at 500 m intervals across the reserve. Overall, the work resulted in seven soil samples, with data collected on both north and south aspects and in different slope positions.
Social ContextBased on the USFS team’s visit, the community in the upper watershed outside the reserve seems to be having an impact on the water flowing into the reserve. Much of the water in the uplands is taken for domestic and agricultural consumption, including qat production. Grazing in the reserve also appears extensive and the grass layer is mostly depleted.
ResultsIn a ravine south of the governor’s house and on a ledge in the canyon nearby, trees appeared to be growing better, with less overstory mortality (Figure 9). Grazing has removed the grass layer. Significant water use uphill for both domestic and agricultural consumption appears to have had a significant impact on the water flowing into the reserve.
Figure 9 Trees on a ledge (bench) just downhill from the cliff at Foret de Day appear to be growing well
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The dieback at Foret de Day is likely caused by a combination of less rainfall in recent years coupled with competing water use uphill from the reserve. Less rainfall is likely a long term climatic trend in an ecosystem that is probably adapted to a unique set of factors with low resiliency. Population pressures on the upper watershed outside the reserve is also causing less moisture availability to the Juniperus stands. From consultation meetings with specialists in-country, the USFS team gathered that during the 1991-1993 civil war, people left this area; when they returned after the war, they found substantial new forest growth. Soil tests revealed no significant abnormalities.
Recommendations
Manage Water Use in the Upper WatershedThe USFS team recommends that the Government of Djibouti seek ways to reduce water consumption in the uplands outside of the reserve. They could potentially compensate or provide alternatives for people cultivating and irrigating those lands. Programs like this have been successful in Mexico and in the Catskills Mountains in New York.
Livestock ManagementSite managers should consider fencing a small area (perhaps 25 m by 25 m) to prevent livestock grazing to evaluate the landscape response to rest from grazing. This response could then guide future livestock management in the reserve.
Long-Term Ecosystem AssessmentOver the long term, Foret de Day may adapt and evolve into a Combretum forest from a Juniperus forest, because of Combretum’s ability to tolerate drier conditions. Methods of propagating and planting Combretum should be researched and implemented.
ConclusionThe USFS team deeply appreciated the opportunity to participate in this assessment visit in Djibouti and looks forward to potential future collaboration with the US Embassy, Department of Defense, and local partners including PRAREV. The team returned from the field on October 26th and briefed the MAEPE-RH/PRAREV team and military personnel associated with the U.S. Embassy. The team delivered a brief PowerPoint presentations with initial findings and recommendations, and used these to spark discussions. PRAREV found the findings validating of their work, but were also interested in the USFS team’s recommendations for improving methods to stabilize soil through fences and tree planting. The US military hopes this work will build good relations with the Djibouti government and military. They will ask the managers of Godorya and Foret de Day to follow the suggestions in this report.
The content of the PowerPoint presentations has been included in this report. Contacts are listed in the tables below.
Name Position
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Beydane Chigie PRAREV Project Coordinator; [email protected] Sufian Mutagoma PRAREV Monitoring and Evaluation Officer; [email protected] Abdi Mahamoud Abdi Economic & Commercial Section, US EmbassyMajor Christopher Hettinger Bilateral Affairs Officer, US EmbassyBen Branoff Ecologist, International Programs, USDA Forest ServiceTom DeMeo Ecologist, International Programs, USDA Forest Service
Table 1. Attendees of the debriefing at the Ministère de l’Agriculture, de L’Eau, de la Pêche, de l’Elevage Chargé des Ressources Halieutiques (MAEPE-RH) office on 26 October 2017.
Colonel Jacob Abrami Embassy Army AttachéMajor Trish Basle Office of Security Cooperation Chief, US EmbassyMajor Christopher Hettinger Bilateral Affairs Officer, US EmbassyBen Branoff Ecologist, International Programs, USDA Forest ServiceTom DeMeo Ecologist, International Programs, USDA Forest Service
Table 2. Attendees of the debriefing at the US Embassy on 26 October 2017. Merry Walker with the US Embassy in Djibouti is the main point of contact for USFS International Programs.
ReferencesBadji, S. 2016. Etude de l’ecosysteme de mangrove de Godorya. Djibouti City, Djibouti: Ministere de l’Agriculture, de L’Eau, de la Peche, de l’Elevage, Charge des Ressources Halieutiques, 85 pp.
CBEMR (Community Based Ecological Mangrove Restoration). 2017. Information sheet. Bangkok,Thailand: CBEMR, 2 pp.
Dharani, N. 2011. Field guide to common trees and shrubs of East Africa. Cape Town, South Africa: Struik Nature, 328 pp.
Enright, J., and S, Kampongsun. 2017. Thailand case study: Community based Ecological Mangrove Restoration (CBEMR). Bangkok, Thailand: Ecosystems Protecting Infrastructure and Communities’ Project (EPIC), 48 pp.
GNF (Global Nature Fund). 2015. Mangrove restoration guide. No publication location, 60 pp.
International Union for Conservation of Nature (IUCN), 2011. Mangroves to Receive Huge Boost from New Carbon Credit Rules. http://www.iucn.org/?7595/Mangroves-to-receive-huge-boost-from-new-carbon-credit-rules (accessed 5 August 2012).
EPA (Environmental Protection Agency). 2010. Guidance for assessing petroleum hydrocarbons in soil. 15 pp. Available on line at www.epa.state.oh.us/portals/30/rules/di-033.pdf
Grubinger, V., and D. Ross. 2011. Interpreting the results of soil tests for heavy metals. Montpelier, VT: Univ. of Vermont Extension, 4 pp.
Tierney, J.E., Ummenhofer, Caroline, C. & DeMenocal, P.B. (2015) Past and future rainfall in the Horn of Africa. Science Advances.
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Witsen, D.B. 2012. Mangrove restoration and management in Djibouti. Blacksburg, VA, USA: Virginia Polytechnic University, M.Sc. thesis, 28 pp.
World Agroforestry Centre, 2002. Agroforestree Database. Nairobi, Kenya: ICRAF. http://www.worldagroforestrycentre.org/Sites/TreeDBS/AFT/AFT.htm.
Appendix 1Data from Godorya mangrove sites 24 Oct 2017. Photos are available from Tom DeMeo on request.
Site Sample Point Lat (North) Long (East)Photo No.
Distance (m) Salinity
1 1 12 deg 9.329 min 43 deg 24.174 min 1 2 41 ppt1 2 12 deg 9.324 min 43 deg 24.167 min 2 101 3 12 deg 9.321 min 43 deg 24.164 min 3 151 4 12 deg 9.316 min 43 deg 24.157 min 4 27 Sample taken1 5 12 deg 9.315 min 43 deg 24.155 min 5 32 38 ppt2 6 12 deg 9.293 min 43 deg 24.231 min 14 4 42 ppt2 7 12 deg 9.287 min 43 deg 24.232 min 9 153 8 12 deg 9.251 min 43 deg 24.258 min 13 1503 9 12 deg 9.326 min 43 deg 24.511 min 18 7 35 ppt3 10 12 deg 9.331 min 43 deg 24.512 min 20 2 45 ppt
Appendix 2Data from Foret de Day sample points 25 Oct 2017. Photos are available from Tom DeMeo on request.
Photo
Sample Point Lat (North) Long (East)Elevation (m ASL) Numbers Distance (m)
11 11 deg 46.215 min 42 deg 39.078 min 1470 37,38,39,40 012 11 deg 46.204 min 42 deg 39.069 min 1466 41,42,43,44 2513 11 deg 46.183 min 42 deg 39.054 min 1462 45,46,47,48 4814 11 deg 46.176 min 42 deg 39.050 min 1461 49,50,51,52 6815 11 deg 46.293 min 42 deg 38.806 min 1481 53,54,55,56 50016 11 deg 46.400 min 42 deg 38.587 min 1468 56,57,58,59 100017 11 deg 46.408 min 42 deg 38.595 min 1466 60,61,62,63 1000
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Appendix 3Sample location maps
Sampling locations in the Foret Du Day National Park (left) and the Godorya mangroves (right). Point coordinates are given by appendices 1 and 2, respectively.
Appendix 4Soil Test Results (delivered January 3, 2018)
The USFS team collected 10 samples at Godorya and seven at Foret de Day. The objective at Godorya was to see if mangrove mortality may have been influenced by high levels of contaminants in the soil. The objective at Foret de Day was to investigate reports that herbicides may have contributed to tree mortality, specifically in the juniper stands. All samples were analyzed by Specialty Analytical, a lab in Clackamas, Oregon.
Soil Test Results—Godorya MangrovesThe lab analyzed 10 soil samples for petrocarbons (diesel, lube oil, and gasoline) and heavy metals (copper, lead, and zinc). Total Kjeldahl nitrogen (TKN) was also analyzed in order to assess whether nitrogen levels were deficient or excessive for plant growth.
Salinity levels from preliminary field tests were a bit high but within a normal range. Sodium correlates strongly with salinity, because of the sodium found in salt. Sodium levels (equivalent to 0.9 to 28 ppt) from the lab tests suggest lower salinity than field results (35 to 45 ppt).
Diesel and gasoline are essentially not present and low levels of lube oil (based on EPA 2010) were found in only 2 of the 10 samples. Copper, lead, and zinc levels were also low, falling within a range consistent with the “unrestricted
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[land] use” category for soils by the New York State Department of Environmental Conservation (Grubinger and Ross 2011). Level of concern thresholds for copper, lead, and zinc are 270 ppm, 200 ppm, and 1100 pm for copper, lead, and zinc, respectively. The Godorya samples showed no more than 59.5 ppm, 4.03 ppm, and 71.9 ppm, respectively, for these elements.
Total Kjeldahl Nitrogen (TKN) values of 85 to 1090 ppm (or 0.09 to 1.0 percent) appear within a range neither in deficit or excess. This does not reflect the actual amount available to plants. Because mangroves are associated with nitrogen fixation, and are very efficient in using and retaining nitrogen, excess nitrogen in this ecosystem would be more of a concern than a nitrogen deficit.
The full lab results are presented in the Table below.
Sample ID
Salinity(ppt)
Sodium Diesel Lube Oil
Gasoline Copper Lead Zinc Total Kjeldahl Nitrogen (TKN)
1 41 894 ND ND ND 40.5 2.84 45.9 1062 9730 ND ND ND 50.5 3.12 62.3 67.53 27700 ND ND ND 41.6 2.93 47.2 854 7150 ND ND ND 59.5 4.03 71.9 1295 38 15000 ND 96.2 ND 40 3.77 48.9 10906 42 8270 ND ND ND 30 2.91 38.7 4187 17800 ND ND ND 32.1 3.88 43.4 1388 11500 ND ND ND 30.5 3.39 41.8 1669 35 12000 ND 115 ND 23.9 1.3 19.9 75810 45 7520 ND ND ND 18.6 0.932 14 575
Table- Results of analysis of Godorya mangrove soil samples. Salinity values were collected in the field; other values come from laboratory analysis. All units are in parts per million (ppm), except salinity, reported in parts per thousand (ppt). ND= No Determination (none).
Soil Test Results- Foret de DayAll seven soil samples collected at Foret de Day showed no evidence of herbicides. The herbicides tested include 2,4,5-T, 2,4,5-TP (Silvex), 2,4-D, 2,4-DB, 3,5-Dichlorobenzoic acid, 4-Nitrophenol, Dicamba, Dichlorprop, Dinoseb, MCPA, MCPP, and Pentachlorophenol. Herbicides were likely not a factor in tree mortality in the National Park.
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