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Abstract
Mangroves are often presented as NbS for,
among others, Blue Carbon. However, a lack of
locally relevant data makes ecosystem service
estimates highly uncertain, and outcomes do
not always benefit local traditional rights
holders. In coastal Ghana, mangroves remain
understudied but overexploited because a
value chain centered on firewood provides
livelihoods to numerous stakeholders. In
MANCOGA, stakeholders from local
communities to national decision makers use
co-design to identify alternative and
sustainable mangrove use. We investigate
effects of current and possible alternative
management on carbon sequestration, and
suitable metrics for issuing carbon credits.
Results indicate a strong positive relationship
between mangrove age after cutting and
carbon density, demonstrating the potential
for Blue Carbon credits; halted deforestation
will lead to reduced carbon emissions and
re/forestation to carbon dioxide removal.
Stakeholder engagement reveals the
acceptability and feasibility of mangrove Blue
Carbon as a sustainable livelihood for
landowners. However, challenges for other
stakeholders at the bottom of the existing
value chain, as well as cultural and economic
factors, including a lack of affordable
alternative fuel sources, inhibit the uptake of
management changes. We regard MANCOGA
as a pilot and aim to scale a successful
intersectoral approach to West Africa and
beyond.
David Kaiser2,
Edem Mahu1,
Benjamin Botwe1,
Fatawo Abubakar1,
Bryce Van Dam2,
Yaw Atiglo1,
Senyo Adzah1,
Annette Ankrah1,
Holger Brix2
Blue Carbon as an alternative livelihood
provided by mangroves in Ghana
21
Background
Mangroves in Ghana are heavily exploited for
wood. Between 1980 and 2006 their area was
reduced from 181 to 138 km² [1], and even
further to just 74.2 km² in the early 2020s [2].
This dramatic decline is inherently
accompanied by a loss of ecosystem
services. Importantly, some of these
ecosystem services may be commercially
exploited in a way that drastically reduces
deforestation and potentially motivates re-
and afforestation. In the existing local
structure of rights and privileges, mangrove
areas are privately owned and owners lease
plots for wood cutting to harvesters. Plots are
traditionally generally harvested on a cycle of
12-15 years, but driven by market profitability
and economic necessities, in many cases the
allowed growing period has been reduced to
less than 10 years [1]. The harvesters
commonly completely denude the plots of
above ground vegetation and, after a period of
wood drying in piles on slightly elevated
ground, ferry the wood to a local market.
There, the wood is sold in bundles or stacks,
rather than by weight. Much of the product is
transported as small-scale cargo to buyers
outside the region. A common use is burning
as firewood, but the mangrove wood is
particularly valued to smoke fish with
because it gives the fish a sought-after
fragrance and color.
Traditional local governance lends these
practices a degree of autonomy that may be
beneficial in re-designing the use of
mangroves without excessive bureaucracy
while providing sustainable livelihoods in
local communities. One possible use would
be the avoided cutting and replanting of
mangrove trees for Blue Carbon credits. This
however poses both academic and social
challenges: 1) the Blue Carbon potential
needs to be rigorously evaluated to ensure its
long-term viability as a source of income, and
2) with a ceasing of mangrove cutting must
come new sustainable and acceptable
livelihoods for all stakeholders along the
former firewood value chain.
[1] UNEP (2007) Mangroves of Western and
Central Africa
[2] Nunoo and Agyekumhene (2022)
Agricultural Sciences , 13, 1057-1079.
Approach
We focus our initial study on the mangrove
area in Anloga district, southeast Ghana,
which is located between the estuary of the
Volta River, Ghana’s largest, and the Keta
lagoon, a Ramsar site. Despite being the
largest contiguous mangrove landscape in
Ghana, there are no primary trees left, but the
oldest are about 25 years old. Most plots age
10-15 years, in accordance with the harvest
cycle.
We compare carbon stock in the existing
mangroves between sites populated by trees
of different ages. For this task we mainly
follow recommendations by Kauffman and
Donato (2012, CIFOR Working Paper 86).
However, the relatively small size of the plots
of any given age means that replicate or
gradient sampling is not often feasible. We
selected plots aged 1, 3, 7, 10, 15, and 25
years. At each plot we measured the diameter
at breast height, either at 130 cm or above the
highest prop root, and height of all trees.
These data were then used to calculate the
above and below ground biomass and carbon
within the plot with allometric equations. At
the same plots we took triplicate sediment
profiles of 1 m depth, which were
subsampled at depths of 0-1, 1-15, 15-30, 30-
50, and 50-100 cm, and measured for organic
carbon content on an elemental analyzer after
acidification. Integrated soil organic carbon
within the top 1 m was calculated as
suggested by Howard et al. (2014, Coastal
Blue Carbon…). The results presented here
must be seen as preliminary; we used one
common equation to calculate carbon from
tree characteristics and will adjust this to
reflect the different species and ages of
mangroves, and we have only analyzed a
handful of our hundreds of soil samples with
the remaining ones following soon.
To gain a better understanding of the social
interconnections around mangrove
management we conducted a Qualitative
Systems Appraisal in the study area. This
social sciences approach included Focus
Group Discussions with well-balanced
contributions from male (8) and female (10)
participants of young and old ages. Our In-
depth Interviews with Key Informants were
less balanced but still included both male
(12) and female (3) experts. The topics
addressed during the interviews mostly
related to the use of mangroves and
included the participants’ understanding of
its dynamics, gender roles and social
relations, power dynamics and decision
making, community benefits and conflicts,
adaptation and change, and future outlook.
In addition, during Transient Walks &
Observations, we appraised the market
valuation and pricing of mangroves.
this map shows our study region in Ghana; the
dashed green frame covers our primary fieldwork
area
Insights
As would be intuitive, the amount of carbon
present in tree biomass increases as the
mangrove ages. We measured an increase of
above and below ground tree carbon with age
that is nearly linear (r2 = 0.72). However, there
appears to be a plateau after 10 years,
possibly due to natural thinning and
maturation of the forest, and tree carbon
seems to increase exponentially in younger
plots; remeasurement of the oldest forests
would be desirable after several years to
establish the increase over time. Because
under current practice we must assume that
there is definitive threat of deforestation to
any mangrove plot older than 15 years, the
definition of avoided emissions for Blue
Carbon would be satisfied if trees were
allowed to grow. However, equally important
is the concept of durability, requiring the
carbon to be fixed for a long time, commonly
defined as at least 100 years [3]. While the
tree biomass of the forest as a whole may
well reach that age and more, the soil is
where carbon may be buried the longest. And
in the Keta mangroves we find high soil
organic carbon content (2.9-22.9%). This
means that even in older mangroves, the top
1 m of soil holds about 10 times the amount
of carbon that is present in tree biomass.
Unlike with tree biomass, soil organic carbon
content does not scale linearly with mangrove
age (r² = 0.42). Nor would it be expected to
because the soil accumulates over many
harvest cycles, and before any initial harvest.
Nevertheless, the average carbon content in
mangroves older than 10 years is 1.64 times
that in young ones, and despite the small
sample size of our preliminary analysis this
difference is statistically significant (t-test
p-value is 0.001).
[3] Fearnside (2002) Mitigation and Adaptation
Strategies for Global Change 7: 19–30
Consequently, avoiding harvests and
(re)establishing mangroves in suitable
locations would greatly increase the
amount of Blue Carbon. The growth of new
mangrove trees and the soil they produce
could therefore become an option for CO2
certification as a sustainable livelihood at
least for mangrove owners. How co-benefits
of healthy mangroves can be translated into
alternative livelihoods for all stakeholders is
a critical issue for the success of possible
mangrove protection and rehabilitation
efforts.
this figure shows the carbon bount trees, both the
above ground and below ground part, and
sediments organic carbon (SOC) in mangroves with
different ages. Note that SOC is devided by 10 for
better visibility of tree carbon.
0
20
40
60
80
100
120
140
160
13710 15 25
years since harvest
above ground C [t/ha]
below ground C [t/ha]
1st meter SOC [t/ha*10]
Our stakeholder interactions show that the
perspectives on mangrove conservation
and management differ by type of
stakeholder. There are diverging themes
generated from interviews with government
agencies and local government entities,
community stakeholders who include
persons in the mangrove value-chain and
traditional authority.
For government agencies, the main
economic benefit is derived, via the district
assemblies, from members of the value
chain, including revenue from levies
charged the mangrove retailers and
transporters at the local market. Mangrove
ownership and management, i.e. growth,
harvesting and use, are largely unregulated.
There is a lack of legal regimes to control
mangrove harvesting or use in Ghana. Local
assemblies and environmental agencies
perceive a lack of capacity (logistics and
authority) to monitor and regulate the
activities of mangrove traders. There is the
need for education and awareness creation,
as well as strict regulations. Conservation
efforts require legal agreements with
mangrove owners and workers, and they
must be adequately compensated and
monitored.
With regards to challenges associated with
the feasibility and acceptability of blue
carbon, local government officials perceive
that their districts/local areas do not qualify
to earn carbon credits, nor do they have
capacity for conserving mangroves. Some
others are not aware of the potential to earn
such carbon credits. In fact, the concept of
blue carbon does not feature in local
assembly planning.
Among community members, particularly
stakeholders in the mangrove value-chain,
there is apprehension about the idea of
regulating mangrove harvest and
conservation of mangroves for blue carbon
credit. For them, conservation efforts must
come with financial/economic benefits to
have their support. There must also be
sustainable livelihood alternatives and
affordable alternative fuel sources if
community members should desist from
harvesting mangroves. Mangroves are the
main source of income, wood fuel and
resources for construction. Alternative
livelihoods must consider the social and
cultural norms and values of the people,
including traditional livelihoods systems,
leadership and taboos. For example,
alternative livelihoods which include
aquaculture have suggested some taboo
species including catfish and shrimp
farming. Some mangrove owners perceive
that blue carbon efforts undermine their
self-efficacy, the power to determine what
to do with their own heritage and not
bequeath it to central government.
In the mangrove trade, the pricing of
mangrove wood is not based on metric
measurements. Mangrove wood is priced
based on size, part of mangrove and wood
quality. However, arbitrary estimation of
wood quantities usually fit in a range. The
more flammable the lower the value. Main
stems have the highest value, and the sub
roots have the lowest. Calculating required
income from alternative livelihoods is thus
complicated.
David measuring tree height Edem measuring tree diameter
What’s Next
The results of the investigations are
still raw, and we have only
performed preliminary data
analyses. Hundreds of sediment
samples will be analyzed, and their
values put into more species- and
site-specific calculations to
improve the accuracy of your
estimates. To add to the common
practice of measuring carbon
stocks in biomass and soil, we will
also identify carbon sources by
analyzing the stable isotope
signature, i.e. the ratio of 12C to 13C,
in our solid samples. Furthermore,
the analyses of water samples for
dissolved inorganic carbon will
allow us to quantify the production
of alkalinity, a possibly important
way that mangroves contribute to
CO2 uptake from the atmosphere.
Social survey results will be
transcribed and analyzed. Of
course, these final results will be
published in scientific journals. To
make them available to
stakeholders that could benefit
from them and to increase their
hand-on impact, we will also
produce educational materials and
policy briefs that describe in
audience-appropriate language
what we find about mangrove Blue
Carbon as an alternative livelihood. Benjamin guiding field trip
Fatawo slicing sediment Bryce collecting sediment
Yaw guiding social science trip
Senyo collecting market data Annette recording field data Holger keeing it all together