Environment

Impact of forest modification and agricultural practices on aquatic ecosystems

By

Okogwu Okechukwu I¹ ; Ngonkeu Mangaptche Eddy Leonard²; Mochiah Moses Brandford³; Chima Uzoma Darlington ⁴ ; Bwala Richard Lema⁵ and Augustus Asmah⁶

1. Applied Biology Department, Ebonyi State University, PMB 53, Abakaliki, Ebonyi State, Nigeria
2. Institute of Agricultural Research for Development PO Box 2067 Yaounde Cameroon
3. Crops Research Institute, P. O. Box 3785, Kumasi, Ghana
4. Department of Forestry & Wildlife Mgt., University of Port Harcourt, Nigeria
5. Environmental Division, National Institute for Freshwater Fisheries Research (NIFFR), P.M.B. 6006, New Bussa, Niger State, Nigeria.
6. Dept of Soil Science, School of Agriculture, University of Cape Coast, Ghana.

Introduction

Recent studies have shown that there is a direct link between land use and water quality. Deforestation exposes the land surface and contributes to soil erosion and nutrient leaching from soils into nearby rivers, lakes and ponds. Increased siltation of rivers and ponds may impact negatively on the quality of these ecosystems. Siltation decreases water depth leading to increase in water temperature, increase in water turbidty and a reduction in water clearity; such conditions will impair light penetration and as a consequence, reduce phytoplankton productivity. Reduced phytoplankton productivity is likely to have a cascading effect on zooplankton, fish productivity and diversity.

Forests especially riparian forests act as a buffer to rivers and other water bodies preventing sediments from contaminating them.Consequently,the replacement of natural forests with other land use types like farmlands, will undoubtedly lead to water quality detrioration, and may impact negatively on fish populations due to modified habitat conditions. Available information also shows that the impact of artificial fertilizers and pesticides on aquatic ecosystems are numerous, difficult to predict and ecosytem dependent. Most researchers have therefore, advocated the use of biofertilizers and biopesticides. Since these are biodegradable, it is believed that the impact on aquatic ecosytems may be minimal and easy to predict. However, there is a dearth of information on the comparative impact of artificial fertilizers and biofertilizers on one hand and artificial pesticides and biopesticides on the other hand accross a broad landscape scenerio. This study will be undertaken to evaluate the impact of deforestation and current agricultural practices on aquatic ecosystems in three countries within the West and central African Regions. Okogwu

Objectives

To determine the impact of current agricultural practices on aquatic ecosystems

Specific objectives

• To determine the effect of deforestation on fish diversity
• To determine the effect of biospesticides application on phytoplankton, zooplankton and fish diversity
• To determine the effect of biofertilizers application and cultivation practices on water quality, phytoplankton, zooplankton and fish diversity

Methodology

Locations

This study will be carried out in three countries: Nigeria, Ghana and Cameroon .

Sites: Two main ecosystems are involved: Forest zones and Farmlands

Agricultural practices of interest: shifting agriculture, application of chemical fertilizers, pesticides, biofertilizers, and biopesticides.

Activity 1: determination of the effect of deforestation on fish diversity

Fish populations will be sampled in both rivers where the sorrounding riparian vegetation has not been modified and where they have been cleared for agricultural purposes, in the three countries comprising the study area.

Simpson diversity index (Simpson, 1949) will be used to ascertain the diversity of fish species in both rivers within natural forests and those in rivers surrounded by farmlands using Past statistical software.

In each country, water samples will be collected from 50 points in rivers near farmlands, and within the natural forest. Chemical Water analysis will be carried out to ascertain the chemical composition of the different water samples, and comparisons made between rivers within natural forests and those around farmlands.Chima

Activity 2: Effect of biopesticides application on phytoplankton, zooplankton and fish diversity

A completely randomized design will be used with the following treatments: (a forest cover, (b) cleared forest, (c) cleared forest with Conventional (Synthethic) pesticides, (d)cleared forest with biopesticides application. Water quality and fish chemical analysis will be determined. Fish biomass and diversity will also be determined.

Activity 3: Effect of biofertilizer application and cultivation practices on water quality, phytoplankton, zooplankton and fish diversity

This activity would evaluate the differences in the concentrations of N, P, and other heavy metals in an aquatic body within a farming community where chemical N and P fertilizer application is a normal practice as compared to the use of a biofertilizer such as mycorrhizal fungal inoculum to enhance phosphorus acquisition and the incorporation of a leguminous cover crop to protect the soil surface and supply N. Biomass densities and diversity of plankton and fish will be correlated with changes in water quality in terms of N, P and heavy metal concentrations due to cultvation practices. A completely randomized design will be used with the following treatments: (a)forest cover, (b) cleared forest, (c) cleared forest with chemical fertilizer, (d) cleared forest with biofertilizer (mycorrhizal inoculum and organic manure) application.

Sorenson's similarity index will be used to measure the plankton diversities between the water bodies.

Expected Output

• Comprehensive understanding on the effects of current agricultural practices on different components of the aquatic ecosystem will be documented.
• Hard facts about the environmental benefits of biofertilizers and biopesticides will be provided.
• Sustainable agricultural practices in the study area will be recommended.