RIASSUNTO
Abstract
Chevron Nigeria Limited (CNL) has embarked on a large-scale mangrove protection and restoration initiative in its operations in the Niger Delta mangrove swamps in Nigeria. Several restoration techniques are applied - natural recolonization, transplanting from local forests and planting collected propagules and seeds. Developing restoration protocols or procedures and testing these protocols on pilot scale precedes each technique. Establishing these restoration protocols assures success when applying these to large-scale restoration. The establishment of restoration procedures for four species of mangrove (Rhizophora racemosa, Rhizophora mangle, Laguncularia racemosa and Avicenia germinans) started in July 1998 and was completed in April 2001. CNL is proceeding to carry out mangrove restoration starting in 2001. About 73 Ha is targeted. This involves applying hydrologic restoration followed by natural recolonization techniques in about 66 Ha, transplanting about 4 Ha of salvaged mangrove seedlings (30 - 60 cm) and salvaged saplings (1 m and 2 m) from a proposed development site and planting another 4 Ha by collecting seeds and propagules. Sites are identified using hyperspectral imageries acquired over CNL's onshore acreage, and targeted sites are along Abiteye - Escravos pipeline Right-of-Way (ROW), Dibi and Olero Creek field, among others in CNL's Oil Mining Lease (OML) -49.
The services of ChevronTexaco Energy Research and Technology Company (ERTC), Lewis Environmental Services (LES) and Environmental Resources Manager Limited (ERML) are employed to establish the procedures and carry out the program. The program collaborates with Nigerian Non Governmental Organizations, including the Nigerian Conservation Foundation (NCF), and the Nigerian Environmental Society (NES). Local community members are involved in the program and given some ownership. Direct and indirect protection of mangrove resources is also carried out at one development site by the establishment of a buffer strip of mangrove along the riverbank to replace the utilization of bulkheads to control erosion.
This paper discusses the procedures established and the large-scale restoration program embarked upon.
Introduction
Mangroves are forests ecosystems specially adapted to saline soil and water conditions.1 In Nigeria, they occur along the flooded tidal muddy plains of the Niger Delta, occupying an estimated 10,000 Km2 from the Benin River in the west to the Imo River in the East (Figure 1). They form part of the extensive wetland vegetation zone (one of six vegetation zones in Nigeria), a zone that occupies an estimated 26,000 Km2. This zone is comprised of a complex hydrology of shallow vegetated tidal flat that includes mangrove forests, tidal marshes and freshwater forests (which occur on slightly higher ground inland of the primary marine and brackish water plant communities).2 There are five species of mangroves in Nigeria, Rhizophora spp (R. racemosa, R mangle and R. harrisonni), Avicennia germinans and Laguncularia racemosa. About 90% of the mangroves in Nigeria are species of Rhizophora and the most common is the Rhizophora racemosa.3 Mangroves can grow to a height of about 25-40m with a girth of 3m. The uses and importance of mangrove have been documented elsewhere.1,3,4
Various human activities have been reported as responsible for the loss of mangrove vegetation in the Niger Delta.2,3,4 The major loss is due to clearing for timber and charcoal production, shrimp farming, tourism development and development of oil reserves which are found in vast quantities in the Niger Delta. Primary and secondary impacts to mangroves can occur from oil development activities, and understanding the complex and fragile nature of mangrove ecosystems to the extent that they affect oil and gas operations is precursor to a successful mangrove protection and restoration program.1,3,4