Djoua-Zadie Forest

Central Africa > Gabon > Djoua-Zadie Forest

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Summary

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• Central chimpanzees (Pan troglodytes troglodytes) & western lowland gorillas (Gorilla gorilla gorilla) are present in Djoua-Zadie Forest.
• In 2016 it was estimated that 2,217 chimpanzees and gorillas occur in the area.
• The population trend is unknown.

Site characteristics

Yeno & Ngoran (2016) suggest that the Djoua-Zadié Forest should undergo a change in its conservation designation. The authors propose to the Gabonese government to reclassify a portion of the forest as a protected area in order to establish a vital corridor for large mammal populations between the Odzala-Kokoua NP (Congo) and Minkébé National Park (Gabon) as this will significantly contribute to regional biodiversity conservation.

Table 1. Basic site information for Djoua-Zadie Forest

Species	Pan troglodytes troglodytes, Gorilla gorilla gorilla
Area	5,444 km²
Coordinates	Lat: 1.1080 , Lon: 13.556
Type of site	Non-protected area
Habitat types	Subtropical/tropical dry forest, Subtropical/tropical moist lowland forest, Subtropical/tropical swamp forest
Type of governance

Types of sites Governance types Habitat types

Ape status

Table 2. Ape population estimates reported for Djoua-Zadie Forest

Species	Year	Occurrence	Encounter or vistation rate (nests/km; ind/day)	Density estimate [ind./ km²] (95% CI)	Abundance estimate (95% CI)	Survey area	Sampling method	Analytical framework	Source	Comments	A.P.E.S. database ID
Pan troglodytes troglodytes & Gorilla gorilla gorilla	2015-2016	Present	1.12	0.407	2,217 (1,390-3,537)	Djoua-Zadie Forest	Line transects & recces	Distance sampling	Yeno & Ngoran 2016	The abundance , as well as the nest encounter rate, of chimpanzees and gorillas was merged	GAB0010

Sampling methods Analytical frameworks

Threats

Table 3. Threats to apes reported for Djoua-Zadie Forest

Category	Specific threats	Threat level	Description	Year of threat
2 Agriculture & aquaculture	2.1.1 Shifting agriculture	Present (unknown severity)	A variety of human activities occur both within the forest and in its surrounding areas, including hunting, fishing, farming, forestry, and artisanal mining. These practices reflect the diverse ways in which people interact with and utilize the landscape (Yeno & Ngoran, 2016).	Ongoing (2015)
3 Energy production & mining	3.2.1 Industrial mining	Low (up to 30% of population affected)	The area holds considerable mining potential, with notable iron deposits such as Belinga and Boka Boka. To address the ecological impact of these mining activities, it is proposed that environmental offsets be implemented. These would include the creation of conservation areas equipped with strong anti-poaching measures, ensuring effective biodiversity protection while supporting industrial development.	Ongoing (2015)
3 Energy production & mining	3.2.3 Artisanal mining	Present (unknown severity)	A variety of human activities occur both within the forest and in its surrounding areas, including hunting, fishing, farming, forestry, and artisanal mining. These practices reflect the diverse ways in which people interact with and utilize the landscape (Yeno & Ngoran, 2016).	Ongoing (2015)
5 Biological resource use	5.1 Hunting & collecting terrestrial animals	Medium (30-70% of population affected)	Since the Djoua-Zadié Forest is not currently covered by the ANPN's (National Agency for National Parks) anti-poaching patrols, it is crucial for the ANPN and the Ministry of Wildlife to urgently develop a strategy for patrolling this area. Utilizing the rivers as a patrol route could be an effective approach to enhance the protection of this vulnerable zone (Yeno and Ngoran, 2016)	2015-Ongoing
5 Biological resource use	5.3.2 Commercial logging	Medium (30-70% of population affected)	Logging companies operating in the area, which is located within the ecological corridor connecting Odzala-Kokoua and Minkébé National Parks must adopt FSC (Forest Stewardship Council) standards. These guidelines promote sustainable forest management, ensuring resource extraction is carried out responsibly while preserving the integrity of these untouched areas and maintaining ecological connectivity.	Ongoing (2015)

Threats

Challenges

Table 5. Challenges reported for Djoua-Zadie Forest

Challenges	Specific challenges	Source	Year(s)
4 Institutional support	4.1 Lack of law enforcement	Yeno & Ngoran 2016	2015-Unknown
4 Institutional support	4.3 Lack of protected area status	Yeno & Ngoran 2016	2015-Unknown

Challenges

Enablers

Table 6. Enablers reported for Djoua-Zadie Forest

Enablers	Specific enablers	Source	Year(s)
4 Institutional support	4.3 Strong transboundary cooperation	Yeno & Ngoran 2016	2015-2024
5 Ecological context	5.1 Ecological characteristics (e.g. terrain) conducive to conservation	Yeno & Ngoran 2016	2015-2024

Enablers

Documented behaviours

Table 7. Behaviours documented for Djoua-Zadie Forest

Category	Behavior	Observation type	Prevalence	Observation dates	Source	Habituation	Species	Comment
	Not reported

Behaviours

Exposure to climate change impacts

As part of a study on the exposure of African great ape sites to climate change impacts, Kiribou et al. (2024) extracted climate data and data on projected extreme climate impact events for the site. Climatological characteristics were derived from observation-based climate data provided by the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP, www.isimip.org). Parameters were calculated as the average across each 30-year period. For 1981-2010, the EWEMBI dataset from ISIMIP2a was used. For the two future periods (2021-2050 and 2071-2099) ISIMIP2b climate data based on four CMIP5 global climate models were used. For future projections, two Representative Concentration Pathways (RCP) were used. RCP 2.6 is a scenario with strong mitigation measures in which global temperatures would likely rise below 2C. RCP 6.0 is a scenario with medium emissions in which global temperatures would likely rise up to 3C by 2100. For the number of days with heavy precipitation events, the 98th percentile of all precipitation days (>1mm/d) was calculated for the 1979-2013 reference period as a threshold for a heavy precipitation event. Then, for each year, the number of days above that threshold was derived. The figures on temperature and precipitation anomaly show the deviation from the mean temperature and mean precipitation for the 1979-2013 reference period.

The estimated exposure to future extreme climate impact events (crop failure, drought, river flood, wildfire, tropical cyclone, and heatwave) is based on a published dataset by Lange et al. 2020 derived from ISIMIP2b data. The same global climate models and RCPs as described above were used. Within each 30-year period, the number of years with an extreme event and the average proportion of the site affected were calculated (Kiribou et al. 2024).

Table 8. Estimated past and projected climatological characteristics in Djoua-Zadie Forest

Value	1981-2010	2021-2050, RCP 2.6	2021-2050, RCP 6.0	2071-2099, RCP 2.6	2071-2099, RCP 6.0
Mean temperature [C]	24.1	25.3	25.2	25.6	26.5
Annual precipitation [mm]	2894	2931	2904	2933	2907
Max no. consecutive dry days (per year)	12.7	10.5	9.5	11.1	10
No. days with heavy precipitation (per year)	7.3	9.2	9.4	9.2	9.8

Table 9. Projected exposure of apes to extreme climate impact events in Djoua-Zadie Forest

Type	No. of years with event (2021-2050, RCP 2.6)	% of site exposed (2021-2050, RCP 2.6)	No. of years with event (2021-2050, RCP 6.0)	% of site exposed (2021-2050, RCP 6.0)	No. of years with event (2070-2099, RCP 2.6)	% of site exposed (2070-2099, RCP 2.6)	No. of years with event (2070-2099, RCP 6.0)	% of site exposed (2070-2099, RCP 6.0)
Crop failure	6	0	4	0	5.5	0	14	0
Drought	0	0	0	0	0	0	0	0
Heatwave	3	100	5.5	100	3.5	100	12	100
River flood	1	1	1	1.14	3	4.74	2	3.18
Tropical cyclone	0	0	0	0	0	0	0	0
Wildfire	29	0.21	29.25	0.2	28.5	0.22	29	0.21

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  Precipitation anomaly in Djoua-Zadie Forest

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  Temperature anomaly in Djoua-Zadie Forest

References

Yeno, S.L. and Ngoran P.K (2016). Rapport d'inventaire de grands et moyens mammifères dans la forêt de Djoua-Zadié, Gabon. WWF report.

Kiribou, R., Tehoda, P., Chukwu, O., Bempah, G., Kühl, H. S., Ferreira, J., …, & Heinicke, S. (2024). Exposure of African ape sites to climate change impacts. PLOS Climate, 3(2), 1-19. doi:10.1371/journal.pclm.0000345

Page created by: Tene Sop Date: 2024-11-28 12:23:00