**5. Vegetation of the region**

The freshwater swamp forest is found in the inland freshwater areas between high forests and the mangrove swamp forest. The vegetation consists initially of species of reed (Phyragnites spp) and Papyrus (*Cyperus papyrus*). Their roots are submerged while the shoots stand above water and the trees which later cover the reed swamps form swamp forests which are poorer species than the forest on dryland. Palm-like raffia (*Raphia hookerii*) are characteristically present, so also are species of cane. The trees show layering and are still rooted with dense undergrowth of shrubs, and lianas where canopy is exposed to light. The eutrophic water (water that is fairly rich in mineral matter) in the area encourages silt soil to be formed which results from the accumulation of predominantly inorganic sediments in which the water is near the surface. There are floating grasses and other creeping plants along the edges of the creeks and rivers which are invaded either by water lettuce (*Pistia stratiotes*) or water hyacinths (*Eichhornia crassipes*).

The Mangrove Swamp Forest is characterized by evergreen trees and shrubs. The plants cover the sheltered muddy areas where land is rapidly encroaching on the sea in the estuarine and deltaic environments. Mangroves play an active role in building upland from the sea, obstructing currents, thus adding humus and raising the ground level seawards. The mangrove trees are essentially halophytes (adapted to saline habitats) receiving low saline water from rivers and higher saline water from the sea at different times of the day and seasonally. Hence, the predominant species in the brackish water zone are the red mangroves Rhizopora racemosa while other species of the red mangroves are found in the freshwater swamps inland. At the eastern margin of Awoye estuary, the vegetation consists mainly of red mangroves (*Rhizopora racemosa*) with white mangrove (*Avecinnia africana*) lining the inner edges of the creeks and along the rivers. Towards the seaside, Paspalum veginatum which after replacing felled mangroves becomes more dominant, sometimes excluding other species on the inner sand banks, with dense undergrowth of scrambling shrubs and trees, such as *Hibiscus tiliaceus*, Chrsobalanus orticulatis, etc. At the back swamp are raffia palms growing in the marshy areas, freshwater creek and along the rivers. The raffia palm is predominant in the area, it is readily available for construction purposes.

However, with active forest removal going on in the northern axis and extensive areas of marsh and mangrove forests being decimated in the southern parts, a large stretch of land along the coastline is now permanently inundated, especially in Ayetoro and Awoye areas. Thousands of peasant populations in so many rural communities are at the risk of a shortfall in their food security and means of livelihood [11]. Research and literature on the extent of degradation on the transgressive mud coast are lacking. Coastal erosion, canalization, inundation, the emergence of coastal grassland and rapid sedimentation of lagoons are some of the degradation processes identified. The increase in offshore exploration activities in the 70s led to more pronouncement of these degradation activities [12].

## **6. Mangroves ecosystem of the region**

The most globally significant ecosystem between tropical rainforest and marine is mangrove. It represents one of the most productive natural ecosystems from the biological perspective. It is home to some unique endangered animal species. Economically, mangrove woods are used for construction works, useful chemical extraction (wood tar, tannin, alcohol, etc.) and furniture making, High quality charcoal and firewoods which are a good source of fuel are also sourced from mangroves. They also serve as nursery areas for marine animals and fish breeding arena.

In the environment, mangroves protect against storms (natural barrier against coastal erosion and tsunami), toxic substances, roots screening out debris, CO2 absorption thereby reducing greenhouse gas and deposition of suspended sediments in water, creating mudflat for more mangrove. From the sociocultural perspective, it serves as a good source of food and medications for communities. Also, they are good environmental indicators for our climate.

The mangrove ecosystem in Nigeria is unique, being part of the Gulf of Guinea's large marine ecosystem, which is the largest in Africa and the third-largest in the world. It covers Lagos State, Ondo State and Niger Delta areas and occupies areas of about 10,000 km2 in a 30–40 km wide belt [13]. Mangrove forests in Nigeria are found on the coast and stretch into the rivers and complex lagoons in several places. Spalding et al. [14] estimate the Nigerian mangrove to be about 10,500 km<sup>2</sup> .

Plants that are usually associated with mangroves include buttonwood tree (Conocarpus), leather fern (*Acrosticum aureum*), hibiscus (*H. tiliaceus*), etc. Nypa fructicans from Singapore was introduced. Mangroves are harvested for consumption to meet the needs of the local communities [15] and are also being utilized as raw materials for industry [16]. Even though the demand has drastically declined, mangrove wood is still extensively used in Nigeria and the extraction of much higher volumes of wood is undertaken exclusively as selection harvesting under license agreements with the competent authorities [13].

Mangroves help protect the coastline from storm damage, wave action and erosion. They stabilize the elevation of land by accretion of sediment and also protect from damaging siltation seagrass beds and coral reefs. If the present level of mangroves depletion in Nigeria is not reduced, its coastal cities like Warri, Port Harcourt and Lagos will be drowned in the next couple of decades [17].

The area is generally inhospitable and difficult to develop. The area is inhabited mainly by fishermen/women and small farmers. The dense vegetation of mangrove forest found in this area has become a source of income generation, a reliable smallscale food processing and fuel wood for domestic usage [18].

## **7. Meteorology of the region**

The meteorological station with long-time data record closest to the region is at Ondo town. Ondo town is about 85 km (north-south direction) from Ayetoro. Ondo town and the coastal communities fall under the same weather influence. Therefore the 30 years of meteorological data (1984–2014) used to characterize the area were based on Ondo town meteorological station and obtained through the central office of the Nigeria Meteorological Agency (NIMET) Lagos. A new meteorological station is now situated at Ayetoro, one of the communities but does not have long time data. In this station, air temperature and humidity, wind direction and rainfall are typically *Climate Change and Anthropogenic Impacts on the Ecosystem of the Transgressive Mud Coastal… DOI: http://dx.doi.org/10.5772/intechopen.105760*

measured at 2 m above the surface on the muddy beach. Wind speeds are measured at 10 m height above the ground surface. Nigeria Meteorological Agency (NIMET) were contacted for information on the climatic data collected at Ondo from 1984 through 2014. The meteorological variables on which records were available were considered individually below;

#### **7.1 Air temperature**

The mean monthly temperature values at Ondo for the period of 30 years are presented in **Table 1**. The highest mean temperature was recorded in February (26.7 ± 0.5°C) while the lowest value was recorded in August (23.95 ± 0.4°C). With an annual mean air temperature of 26.86 ± 1.3°C, the year 2013 was the warmest year of the 30 years covered in the available record. The coldest year was 1991 with 25.2 ± 1.4°C annual mean value (**Table 2**). On the whole, a short mean air temperature range of 1.66°C was recorded.

#### **7.2 Relative humidity**

The monthly percentage relative humidity (% RH) from 1984 through 2014 was presented in **Table 1**. Relative humidity followed the same pattern as temperature. The lowest relative humidity for the months was recorded in January (68.16 ± 10.0%) while the highest value was recorded in August (90.6 ± 2.7%). The lowest annual relative humidity was recorded in 1984 (79.25 ± 10.0%), while the highest annual mean value of 87.42 ± 5.74% was recorded in 2014 (**Table 2**).

The high humidity experienced in this region makes the air to be close to saturation and thus with less capacity to store additional water. This tends to reduce the rate of evaporation despite high temperature and high energy input in the region. For humid conditions, the wind can only replace saturated air with slightly less saturated


#### **Table 1.**

*Monthly meteorological data of the study area.*



**Table 2.**

*Annual meteorological data of the study area.*

*Climate Change and Anthropogenic Impacts on the Ecosystem of the Transgressive Mud Coastal… DOI: http://dx.doi.org/10.5772/intechopen.105760*

air and remove heat energy [19]. It is noteworthy that the relative humidity in the area in 1984 (about 75%) has increased steadily over a period of 30 years to 90% in 2014.

### **7.3 Rainfall**

The mean monthly rainfall from 1984 through 2014 is shown in **Table 1**. This area experiences a double maxima rainfall regime characterized by two high rainfall peaks. The rainy season begins around March (102.35 ± 53.3 cm) and attains a peak in June or July.

This first peak is followed by a short dry break in August (183.6 ± 107.3 cm), known as the August break usually lasting for about two to 3 weeks in August. This break is usually followed by the resumption of the rainy season and lasts to mid-October with a second peak usually in September. The period from late October through early March constitutes the dry season. The annual highest mean rainfall was recorded in 1985 (211.86 ± 171.39 cm) and the annual lowest mean was in 1990 (113.12 ± 88.36 cm) (**Table 2**). This coastal zone is characterized by high rainfall, with rainfall all the months of the year and annual variability of approximately 113–211 cm as indicated in the 30-year data record.

#### **7.4 Wind speed over the region**

The mean monthly wind speed, which is shown in **Table 1**, revealed a lower wind speed in the dry season (October to February) and which was classified as Light air with the range from 0.5 to 1.6 m/s (according to Beaufort wind speed classification). Also, the rainy season (March to September) experienced a higher wind speed (1.7–2.24 m/s) which was classified as Light breeze according to Beaufort wind speed classification. **Table 1** showed a downward progression of wind speed from 1984 through 2002 and an eventual steady increase from 2002 through 2014. Light breeze (2.99 ± 0.9 m/s) was recorded as the highest annual wind speed in 1986 while 0.77 ± 0.39 m/s (Light air) was recorded in 2002 as the lowest annual wind speed.

#### **7.5 Wind direction**

It is observed that the predominant wind in the study area during the period of study was the southwestern trade wind which originate from the Atlantic Ocean. The southwestern trade wind was predominant for 26 years of the annual record while western and southern trade winds were predominant only in 3 years and a year respectively. Moderate wind was also predominant in the study area.
