Local community knowledge on the impact of climate change on mangroves and livelihoods

MINISTRY OF EDUCATION AND TRAINING
NHA TRANG UNIVERSITY

AFURE WHYTE OLUOWO

LOCAL COMMUNITY KNOWLEDGE ON THE IMPACT OF
CLIMATE CHANGE ON MANGROVES AND LIVELIHOODS:
CASE STUDY OF EKPAN MANGROVE FOREST, DELTA
STATE NIGERIA

NORHED MASTER THESIS

KHANH HOA -2018


MINISTRY OF EDUCATION AND TRAINING
NHA TRANG UNIVERSITY

AFURE WHYTE OLUOWO

LOCAL COMMUNITY KNOWLEDGE ON THE IMPACT OF
CLIMATE CHANGE ON MANGROVES AND LIVELIHOODS:
CASE STUDY OF EKPAN MANGROVE FOREST, DELTA
STATE NIGERIA

NORHED MASTER THESIS
Major:

Marine Ecosystem-Based
management and climate change

Topic allocation decision:
Decision on establishing the
committee:
Defense date:
Supervisors:
TERNEY PRADEEP
KUMARA(Ph.D.)
NGUYEN LAM ANH(Ph.D.)

06/06/2018
Signature

Chairman of committee:
Faculty of graduate studies:
HOANG HA GIANG

KHANH HOA-2018


UNDERTAKING
I undertake that the thesis entitled: “Local community knowledge on the impact of
climate change on mangroves and livelihoods: case study of Ekpan mangrove forest,
Delta state, Nigeria” is my own work. The work has not been presented elsewhere for
assessment until the time this thesis is submitted.
28/04/2018

AFURE WHYTE OLUOWO

iii

ACKNOWLEDGMENT
I want to use this opportunity to thank God Almighty for His grace to complete this
program successfully, although it has not been an easy journey but there were good
people in all sphere ready to assist whenever we needed one. At this juncture, I would like
to express my deepest appreciation to the NORHED program management board, the
Rectorate board, department of international cooperation, faculty of graduate studies and
all lecturers and staff of Nha Trang University who played a part in ensuring a smooth
running of the program, their unending support provided best possible conditions for me
to complete my studies. My special thanks go to Terney Pradeep Kumara (Ph.D) and
Lam Anh Nguyen (Ph.D) for their unrivaled guidance during my study, research and
report writing. Their patience, motivation, inputs and professional experience helped me a
great deal towards actualizing this great feat.
I would also like to acknowledge the management and staff of Centre for Environment
and Sustainable Livelihood Projects Nigeria (CESLP) for the role played during data
collection, collation and gaining community’s willingness to participate in the studies,
really it wouldn’t have been possible without its energetic management and staff
members. In the same vein, my deepest gratitude goes to my friends Isaac Sarfo, Freeman
Elohor for their continuous support and the entire NORHED 2016 class for making my
study time worthwhile.
Last but not the least, I would like to thank my family: my parents and to my brothers for
supporting me spiritually in prayers and kind words throughout my program.
Thank you all!

28/04/2018

Afure Whyte Oluowo

iv

TABLE OF CONTENTS
Undertaking …………………………………………………………………………........iii
Acknowledgment ……………………………………………………………………........iv
Table of contents...………………………………………………………………………...v
List of symbols ………………………………………………………………..................vii
List of abbreviations……………………………………….…………………………….viii
List of tables ……………………………………………………………………………...ix
List of figures ……………………………………………………………………………..x
Abstract………………………………………………………………...............................xi

CHAPTER 1. INTRODUCTION
1.1

Background of study……………………..………………………………………2

1.2

Purpose of study/objectives………………………………………….……………4

1.3

Research questions…………………………………………………….................4

1.4

Significance of the study……………………………………………………….....5

CHAPTER 2. LITERATURE REVIEW
2.1

Climate change in Nigeria………………………………………………………..7

2.2

Vulnerability of mangroves to climate change………………………………….15
2.2.1 Changes in temperature…………………………………………………..15
2.2.2 Changes in atmospheric chemistry……………………………………….16
2.2.3 Changes in Ultra Violet………………………………….………………..17
2.2.4 Sea level rise……………………………………………………………….17
2.2.5 Physical disturbance- tropical storm……………………………...............18
2.2.6 Rainfall and river plumes………………………………………………….19
2.2.7 Changes in ocean circulation……………………………………...............20

2.3

Combined effect of different influences…………………………………………..20

2.4

Impact of climate change on community livelihood……………………..............21

2.5

Adaptation……………………………………………………………..…………22
v


2.6

Status of Niger-Delta mangroves……………………………………………….23

CHAPTER 3. METHODOLOGY
3.1

Study Area……………………………………………………………………….25

3.2

Study site………………………………………………………………...............27

3.3

Research instrument / design…………………………………………………….27
3.3.1 Data collection…………………………………………………………….28
3.3.2 Data analysis………………………………………………………………29
3.3.3 Limitation of study……………………………………………………….29

CHAPTER 4. RESULTS AND DISCUSSION
4.1

Demographic characteristics of respondents…………………………………….31

4.2

Awareness on mangrove and benefits…………………………………………….36

4.3

Awareness on climate change and its impacts……………………………………38

4.4

Adaptive strategies employed by the locals………………………………………42

4.5

Management of the mangrove forest……………………………………………..46

CHAPTER 5. SUMMARY CONCLUSION AND RECOMMENDATIONS
5.1

Summary…………………………………………………………………………..49

5.2

Strengths and weaknesses…………………………………………………………50

5.3

Recommendations………………………………………………………………...51

LIST OF REFERENCES………………………………………………………………...52
APPENDICES

vi


LIST OF SYMBOLS
1. %: Percentage

2. CO: carbon monoxide
3. CO2: Carbon dioxide
4. CH4: Methane
5. Km2: square kilometer
6. mm/yr: millimeter per year
7. Cm: Centimeter
8. oC: Degree centigrade(unit of temperature)
9. N: Naira( Nigeria currency)

vii


LIST OF ABBREVIATIONS
1.

NEMA: National Emergency Management Agency

2.

NIMET: Nigerian Meteorological Agency

3.

NEST: Nigerian Environmental Study/action Team

4.

NPC: National Population Commission

5.

FGD: Focus Group Discussion

6.

IPCC: Intergovernmental panel on climate change

7.

SPREP: Secretariat of the Pacific Regional Environment Programme

8.

UNEP: United Nations Environment program

9.

DESOPADEC: Delta State Oil producing areas commission

10.

NDDC: Niger delta development commission

11.

NGOs: Non-governmental organizations

12.

CBOs: Community based organizations

13.

NDES: Niger Delta Environmental survey

14.

GHG: Green House Gas

15.

BNRCC: Building Nigeria’s Response to Climate Change

16.

CIDA: Canadian International Development Agency

17.

SLR: Sea level rise

18.

CC: Climate change

19.

MDGs: Millennium Development goals

20.

CREDC: Community Research and Development Centre

21.

NASPA-CCN: National Adaptation Strategy and Plan of Action on Climate
Change in Nigeria.

viii


LIST OF TABLES
Table 2.1

Summary of key trends in climatic parameters for Nigeria……………….15

Table 4.1

Demographic characteristics of respondents…………………………........35

Table 4.2

Benefits obtained from the mangrove as listed by participants FGD/open
forum………………………………………………………………………37

Table 4.3

Understanding climate variability and change…………………………….39

Table 4.4

Respondents response on impact of climate change……………................41

Table 4.5

Some adaptive/coping strategies used by the locals……………………….44

Table 4.6

Frequency of event and source of assistance………………………………46

ix


LIST OF FIGURES
Figure 2.1

pattern of onset and cessation of rainfall in Nigeria………………………...8

Figure 2.2

Projected increase in maximum daily temperature across Nigeria……......10

Figure 2.3

Projected change in average daily rainfall over Nigeria………………......11

Figure 2.4

Projected length of the rainy season by zone………………………….......12

Figure 2.5

Projected changes in extreme heat days/heat wave days……………….....13

Figure 3.1

Map of the Niger Delta showing salinity limits/veg. of the coastal zone…26

Figure 3.2

Conceptual framework for the study………………………………………28

Figure 4.1

Gender of the respondents…………………………………………….…...31

Figure 4.2

Age distribution of the respondents……………………………………......32

Figure 4.3

Marital status of respondents…………………………………………..…..33

Figure 4.4

Educational status of the respondents……………………………………..34

Figure 4.5

Awareness of the benefits of mangroves………………………………......36

Figure 4.6.

Respondents level of awareness on climate change…………………….....38

Figure 4.7

Extent of climate change knowledge among respondents…………………39

Figure 4.8

Frequency of climate change event in the study area……………………...40

Figure 4.9

Response during natural disaster…………………………………………..43

Figure 4.10 Alternative source of livelihoods………………………………………….44
Figure 4.11 Respondents view on existence of a management system………………...47
Figure 4.12 Perceived management systems…………………………………………...48

x


ABSTRACT
Mangroves are a taxonomically diverse group of salt-tolerant, mainly arboreal flowering
plants that grow primarily in tropical and subtropical regions. They are known to provide
different ecosystem services and means of livelihood to local communities who are now

faced with changing climate. The study looks into the awareness of local people in Ekpan
community on the benefits of mangroves, their knowledge on impacts of climate change
on the mangrove and livelihoods along with initiated adaptation strategies. The study
employed qualitative techniques using well-structured questionnaires, interviews, focus
group discussions among other strategies to obtain the needed information. The data
obtained was subjected to descriptive statistical analysis. The study results shows the
local people are aware of numerous direct and indirect benefits of mangroves impacting
positively on people’s livelihoods. Flooding, being a single large scale climate event is
frequently experienced in the area with several consequences affecting the health of
mangroves and welfare of the people. Presently, a number of individual coping strategies
have been initiated and needs massive support from key stakeholders in enhancing
adaptive capacity to existing climate hazards in the area.

Keywords: Climate change, impact, mangroves, livelihoods, Ekpan, Niger Delta.

xi


CHAPTER ONE
INTRODUCTION
1.1

Background of study
Mangroves are a taxonomically diverse group of salt-tolerant, mainly arboreal,

flowering plants that grow primarily in tropical and subtropical regions (Ellison &
Stoddart 1991). These ecosystems are known to provide different ecosystem services such
as regulation of climate, water purification, storm control and storm barriers, as well as
habitats for mollusks, crustaceans, water birds and varieties of fishes.
The usefulness of these ecosystems is currently threatened by climate change variability

heightened by growing human pressure on the environment. Alongi (2014) rightly
described mangroves as economically diverse plants rich in value in the form of trees,
shrubs, palm or ground fern, generally not exceeding half a meter in height and which
grows above mean sea level in the intertidal zones of marine coastal environments, or
estuarine margins (Duke 1992). The most commonly known mangrove trees in the Niger
Delta region of Nigeria are; Rhizophora racemosa, Rhizophora harrisonii, Rhizophora
mangle, Avicennia marina, Ceriops tagal, Rhizophora mucronata and white mangrove;
the Rhizophora racemose occupies the greatest density of the forest, thereby accounting
for approximately 90% of all mangrove biota (Abere & Ekeke, 2011).

These mangroves are distributed latitudinally within the tropics and subtropical areas,
reaching their maximum development between coordinate 25°N and 25°S (Hensel et al.,
2002), basically existing in about 118 countries and territories worldwide (Giri et al.
2011) with an estimated size not less than 170,000 km2 (Field, 1995), of which Nigeria
can boast of about 10% area cover after Indonesia with 30%. These unique ecosystems
are abundant and characterize the Nigeria Niger Delta, which is predominant in the
following Nigeria states; Bayelsa, Delta, Cross river, Ondo, Edo, Akwa-Ibom and Rivers
(Mmom and Arokoyu, 2010). Sadly, these precious ecosystems are currently experiencing
high level disturbances mainly from anthropogenic influences widely attributed to clearcutting for agricultural purposes, sand filling, land reclamation for human habitation,
2


deforestation as well as oil exploration to extraction uses known to degrade these vital
ecosystems (Nwosu and Holzlohner, 2016). Nwosu and Holzlohner (2016), reported a
new estimate of 10,515km2 for the Nigeria mangrove, from the earlier estimate of 11,134
km2 in 1997 (Spalding et al., 1997), implying a loss of about 5.6% of the total mangrove
area to both natural and anthropogenic disturbances.

Although the anthropogenic disturbances have been reported extensively to be the major
cause of global ecosystem losses, these activities which constitutes mainly livelihood

options and economic sustenance processes end up disrupting the ecosystem stability,
thereby weakening their resilience and resistance to climate change impacts such as storm
surges and other extreme weather events making mangroves more vulnerable.

The growing impacts of climate change will likely have a substantial effect on mangrove
ecosystems through extreme weather events and processes such as sea level rise (SLR),
changing ocean currents, increasing storminess and temperature, changes in precipitation
as well as CO2 concentration (Gilman et al., 2008; McKee et al., 2012). The occurrence of
one or more of these processes can cause substantial changes in fish population and
species distribution and the worrisome migration of endemic species, invasion of
underwater species, loss of wildlife habitat, intrusion of saline water, and the landward or
seaward movement of mangroves (Gilman et al., 2008), with an overall impact on the
communities that solely depend on their services for survival.
Although, there are robust studies on Nigeria mangroves and noteworthy to the present
study is the investigation of community structure of crustacean zooplankton in Ekpan
creek, a perturbed tributary of Warri River, Niger Delta, Nigeria (Imoobe et al., 2008).
Heavy metal pollutants in Warri River Nigeria (Ayenimo et al., 2005), A preliminary
investigation of heavy metals in periwinkles from Warri River Nigeria (Ayenimo et al.,
2006). Heavy metals and macroinvertebrate communities in bottom sediments of Ekpan
creek (Olomukoro & Azubuike 2009), mangrove forest depletion, biodiversity loss and
traditional resources management practices in the Niger Delta, Nigeria (Mmom &
Arokoyu 2010). Changes in species diversity due to dredged spoils in the mangrove forest
3


of the Niger Delta, Nigeria (Ndukwu and Edwin 2007). Assessment of heavy metals in
surface water and bottom sediment of Ekpan Creek, Effurun, Delta State, Nigeria
(Oluowo & Isibor 2016) and effects of climate change through temperature increase on
heavy metals concentrations in water and sediment of Ekpan creek, Delta State, Nigeria
(Oluowo et al., 2017)

amongst others. These studies mostly delved into the

richness/abundance of species, water quality, heavy metal bioaccumulation, impact of oil
spill and other anthropogenic activities on the forest and its resources, however, not much
have been conducted with regards to climate change related issues on the forest
ecosystem and consequences on the livelihood of the communities, except the work of
Oluowo et al., (2017) which investigated the overall impact of climate change through
temperature increase on heavy metals and sediment of the study area. Recognizing this
knowledge gap, the present study is designed to assess the local community’s knowledge
on the impact of climate change on Ekpan mangrove and on their livelihoods.
1.2

Objectives

The overall aim of the study is to assess the knowledge of the local community on the
impact of climate change using Ekpan community as a case study. The study is to;
1. Evaluate the inhabitants’ awareness on the benefits of mangrove.
2. Assess the knowledge and awareness level of the local people on climate
variability/change and the impacts on their livelihoods.
3. And finally, analyze some of the adaptive strategies employed by the community
to cope with some of these changes.
1.3

Research questions
In line with the objectives, this study also addresses and answers the following

research questions;
•

Are the locals benefitting from the mangrove resources?

•

Are they aware of climate change events and their impacts on mangrove ecosystem
(s) and their livelihoods?

•

What are their adaptation strategies?
4


•
1.4

Is there any form of mangrove/forest management in place?
Significance of the study

The study will help to understand some of the impacts of climate variability on Ekpan
community and their livelihood, and the available mangrove management option (s).
Furthermore, the study result is expected to become a helpful management tool for
government in policy formulation and livelihood provision for mangrove communities in
Nigeria and climate change management.
The study result will encourage conservation initiatives and other management options in
mangrove areas in Nigeria Niger Delta as currently there is limited attention in this area
as compared to terrestrial forest land.
This study also acknowledge the need for more in-depth assessment and scientific
investigation by researchers, government, international aid organizations and NGO’s alike
of the impacts of climate change on mangroves.

5


CHAPTER TWO
LITERATURE REVIEW
Climate change has the potential to affect all natural systems thereby making it a
threat to human development and survival socially, politically and economically
(Raymond &Victoria 2008). Human activities such as burning of coal, oil and natural gas
exploration and exploitation, deforestation, industrialization and poor agricultural
practices have been reported to severely alter the equilibrium and composition of the
environment, thus contributing unwittingly to climate change. These anthropogenic
activities have led to an increase in the atmospheric concentrations of a number of
greenhouse gases such as CO, CO2, and CH4, which have been reported to have both
health and ecosystems implications (Christopher et al., 2006; Akinro et al., 2008; Ball et
al., 1997).
Global climate change is one of the greatest challenges facing this century with reports of
abnormal temperature rise and its attendant impacts on the ecosystem including man
(IPCC, 2007). Although previous geological records has indicated climatic changes
throughout history, human quest for development through industrialization has
unwittingly increased the warming of the earth(IPCC 2007) with huge loss to mangrove
areas and other ecosystem survival.
According to Gilman et al., 2008, climate change components such as high water events
storminess, precipitation, temperature, atmospheric CO2 concentration, ocean circulation
pattern, sea level rise, the health of functionally-linked neighboring ecosystem and human
responses to climate change would have varying impacts on mangroves, which have been
attributed to the robustness and resilience of the system.
Mangroves and their associated coastal systems perform numerous functions important to
the sustenance of coastal communities and countries economic well-being. Some of the
services which could be direct or indirect support traditional practices such as sourcing

for traditional medicines, fuel wood, building materials and natural dyes amongst others
(Gilman et al., 2006, SPREP, 2009) including climate regulation. In the course of
6


collecting these materials, several distortions are created to existing ecosystems which
eventually affect the overall health of the mangroves.
2.1. CLIMATE CHANGE IN NIGERIA
Climate change is an issue of global concern affecting countries in unique ways,
whilst some experience drought others may experience flooding and other extreme
weather events such as; storms and hurricanes (IPCC, 2007). This trend also varies within
countries as most northern parts experience dryness whilst southern parts with coastal
zones are faced with floods as is the case of Nigeria and other African countries. In the
light of this, countries are taking measures to better understand these trends in other to
ensure safety of lives, properties, sustained livelihoods as well as to ensure food security.
To this effect, governments sign treaties, enact laws and become party to several
conventions all in efforts to get better frameworks to tackle this global challenge.
Nigeria has in recent times made several moves to address this challenge by making laws
and establishing formidable bodies within and outside the government to conduct
research, provide data, analyze trends and give possible future projections and impact on
several sectors in line with global scenarios. One of such body is the Nigerian
Meteorological Agency (NIMET) charged with the responsibility to advise the Federal
Government on all aspects of meteorology; project, prepare and interpret government
policy in the field of meteorology; and to issue weather (and climate) forecasts for all
relevant sectors of the economy for sustainable socio-economic activities in the country.
Since its establishment in 2003, NIMET has provided data on temperature, rainfall, on set
of growing season and cessation, little dry season (LDS) among others for the various
regions in the country and their implication for all sectors through its monthly, quarterly
and annual bulletins.
NIMET in 2008 stated that from all indication and observations, Nigeria’s climate is

already changing as they assessed the climate over the period of 1941 to 2000 which they
observed some key changes as compared to previous periods. They noted that during the
period from 1971 to 2000 the combination of late onset and early cessation shortened (fig
7


2.1), which reduced the length of the rainy season in most parts of the country and
between 1941 and 2000, annual rainfall decreased by 2-8 mm across most of the country,
but increased by 2-4 mm in a few places especially the Niger Delta (NIMET, 2008).
(A)

(B)

(source: NIMET, 2008)

Fig.2.1. (A) Pattern of onset of rainfall (B) Pattern of cessation of rainfall

For temperature, there were substantial evidence of long-term temperature increase in
most parts of the country from 1941 to 2000, the main exception was in the Jos area
8


where a slight cooling was recorded. The most significant increases were recorded in the
extreme northeast, extreme northwest and extreme southwest, where average
temperatures rose by 1.4-1.9oC (NIMET, 2008).
There is increased awareness of climate variability and change in the country, as its
potential to bring about damaging and irrecoverable effects on infrastructure, food
production, livelihoods and water supplies, in addition to possible natural resource
conflicts, makes it a critical challenge to any economy seeking sustainable growth. The
government realization of this fact saw its incorporation into the development agenda of

the nation up till year 2020 (Nigeria Vision, 20:2020) and the establishment of a special
climate change unit within the Federal ministry of Environment (FME). Huge support has
also been given to several projects like the building of Nigeria’s response to climate
change (BNRCC) project aimed at developing a National adaptation strategy and plan of
action on climate change for Nigeria (NASPA-CCN).
The BNRCC project was executed by two Canadian firms in partnership with the Nigeria
Environmental study/action team (NEST) and funded by the Canadian international
development agency (CIDA). To actualize a comprehensive action plan for the nation,
this project made future climate change patterns using climate scenarios. This was
possible by commissioning the Climate Systems Analysis Group at the University of
Cape Town to develop climate scenarios for Nigeria by employing empirical approach
using the statistical downscaling method (BNRCC, 2011). Trends in the past climate over
Nigeria were investigated by analyzing the historical climate records from 40 NIMET
stations for the period 1971 to 2000 which was earlier stated; and future climate change
information was generated by downscaling two future climate projections from nine
Global Climate Models. The two future climate projections were based on two scenarios
known as A2 and B1, with A2 incorporating higher greenhouse gas (GHG) emissions,
and B1 lower GHG emissions. The higher global GHG emissions scenario (the A2
scenario) was selected as the strongest. As per their analysis, the scenarios suggest a
warmer climate in the future where the A2 scenario projects a temperature increase of
0.04oC per year until year 2046-2065 (fig. 2.2), rising to 0.08oC per year after 2050.
9


However, they acknowledged regional variations to occur, with the highest increase
(4.5oC by 2081-2100) projected in the northeast.

(Source: NIMET, 2008)

Fig.2.2. Projected increase in maximum daily temperature across Nigeria (presented

in oC relative to the present day climate)
The projection for changes in rainfall also varied across the country, with the A2 scenario
suggesting a wetter climate in the south, as a result of increased evaporation from the
ocean leading to rainfall once all conditions necessary to trigger precipitation are intact,
but a drier climate in the northeast. For the period 2046-2065, the projected change ranges
from an average increase of 0.4 mm per day in the south (15 cm annually) to an average
decrease of 0.2 mm per day (7.5 cm annually) in the north (fig 2.3).

10


(Source: NIMET, 2008)

Fig.2.3. Projected change in average daily rainfall over Nigeria (mm/day relative to
the present day)

This scenario further buttressed into possibilities of extreme events in the different
vegetation zones that is, the mangrove, rain forest and savanna. The A2 scenario for the
period 2046-2065, suggests a small increase in extreme rainfall days (i.e. days with more
than 50 mm of rain) but a small decrease in extreme rainfall days in the Sahel as shown in
fig. 2.4.

11


(Source: NIMET, 2008)

Fig. 2.4. Projected length of the rainy season by zone

The number of extreme heat days and heat waves is bound to increase (fig 2.5) with

temperature reaching 38oC or more increasing to 7 days per year in the mangrove, 23 days
per year in rain forest, 41 days per year in tall grass savanna, and 88 days per year in the
short grass savanna.

12


(A)

(B)

Days

(Source: NIMET, 2008; BNRCC, 2011)

Fig.2.5. Projected changes in (A) extreme heat days (B) heat wave days for the same
time period(Actual 1981-2000 and projected 2046-2065) by zone
13


With regards to sea level rise, as per the expected changes in temperature, rainfall,
and extreme weather events noted above and summarized in table 2.1, this will be an
issue especially in the coastal parts of the country. According to the IPCC projection, sea
levels will rise as a result of increasing global temperatures via a number of mechanisms,
including thermal expansion of water (IPCC, 2007). The global average rate of sea level
rise during the period 1993 to 2003 was about 3.1 mm per year and is expected to
continue, possibly with increases between 18 and 59 cm by the end of this century (IPCC,
2007). If considering this from the upper end of the scale, large areas of Nigeria’s coast
hosting the mangrove areas which is of major concern to this study will be significantly
exposed to increased erosion, storm damage, inundation in low lying areas, among other

impacts.
These incidences are already occurring in the Niger Delta (Okon and Ekpan,1999;
Uyigue and Agho 2007; Amadi and Ogonor, 2015) and are bound to worsen as the
Nigerian Environmental Study/Action Team (NEST) warned in a report in 2004 that the
sea level rise and repeated ocean surges will not only worsen the problems of coastal
erosion that is already a menace in the Niger Delta region but associated inundation will
increase problems of floods, intrusion of sea-water into fresh water sources and
ecosystems destroying such stabilizing systems such as mangrove leading to loss of viable
agricultural lands, fisheries and general livelihoods.

14


Table 2.1. Summary of key trends in climate parameters for Nigeria, by ecological
zone

(Source: BNRCC, 2011)
Table 2.1 depicts key trends in climate parameters for Nigeria in its various ecological
zones. The table illustrates key climatic variables and the extent to which these variables
are increasing or decreasing over a period of time in respective ecological zones.
2.2. Vulnerability of mangroves to climate change
2.2.1. Changes in temperature
Temperature is believed to be the main controlling factor for mangrove
distribution, especially those extending into the latitudinal limits of 32oN and 40oS have a
limited area (Stuart et al., 2007). Apart from distribution, temperature also determines
productivity of mangroves through two key productivity controlling processes;
photosynthetic carbon gain and respiration, processes which are highly sensitive to
temperature changes. It is believed that in most tropical climate, photosynthesis is limited
by high mid-day leaf temperatures resulting in stomatal closure due to higher vapour
pressure deficit between the leaves and air (Clough & Sim 1989, Cheeseman 1994,

Cheeseman et al., 1997). Contrarily in the southern latitudes, photosynthesis is limited by
low temperatures. Worthy of note in the present study is the fact that, the effect of
15