TABLE OF CONTENTS

TITLE PAGE        –         –         –         –         –         –         –         –         i

CERTIFICATION           –         –         –         –         –         –         –         ii

DEDICATION      –         –         –         –         –         –         –         –         iii

ACKNOWLEDGEMENTS       –         –         –         –         –         –         iv-v

TABLE OF CONTENTS          –         –         –         –         –         –         vi-viii

CHAPTER ONE

1.0 INTRODUCTION –         –         –         –         –         –         1-4

CHAPTER TWO

2.0 OVER EXPLOITATION –         –         –         –         –         5-6

2.1 History of over exploitation –         –         –         –         –         6-8

2.2 Over exploitation of common natural resources –         –         8

2.2.1 Fisheries –         –         –         –         –         –         –         –         8-9

2.2.2 Water Resources –         –         –         –         –         –         –         9-10

2.2.3 Forest resources –         –         –         –         –         –         –         11

2.3 Endangered species –         –         –         –         –         –         12-15

2.4 Effect of over exploitation –         –         –         –         16-17

2.5 Threats to biodiversity –         –         –         –         –         –         17

2.5.1 Invasive alien species –         –         –         –         –         –         17

2.5.2 Over exploitation –         –         –         –         –         –         –         18

2.5.3 Pollution –         –         –         –         –         –         –         –         18-19

2.5.4 Climate –         –         –         –         –         –         –         –         19-20

CHAPTER THREE

3.0 RESURGENCE IN INDIGENOUS –         –         –         –         21-22

3.1 Importance of Biodiversity –         –         –         –         –         22

3.1.1 Human health –         –         –         –         –         –         –         23-24

3.1.2 Agricultural –         –         –         –         –         –         –         24-27

3.2     Factors contributing to Resurgence      –         –         –         –         27

3.2.1  Suppression of natural enemies  –         –         –         –         –         27-28

3.2.2  Insecticide-Induced plant growth         –         –         –         –         28-29

3.2.3  Feeding rate           –         –         –         –         –         –         –         29

CHAPTER FOUR        

4.0 SUMMARY AND CONCLUSION

4.1 Summary –         –         –         –         –         –         –         –         30-31

4.2 Conclusion –         –         –         –         –         –         –         –         31-32

References

CHAPTER ONE

1.0 INTRODUCTION

Change is ubiquitous in natural system because the environment conditions that affects biota are also variable. Sea grass and associated submersed aquatic vegetable (SAV) communities in particular, undergo episodes of decline and recovery that spans seasons to multiple decades. Report of decline dominate the literaute with many examples of SAV   loss attributed to chronically degraded water quality associated with eutrophication (Kemp  et al., 1993). Or extreme water events such as hurricanes,  flooding and temperature stress (Preen  et al., 1995).,recent studies, however, have also reported instances of SAV recovery. Most relate expanded plant cover to improve water clarity resulting from management actions such as sewage treatments plant upgrades (Burholder  et al., 2007) . climate related factors such as decrease storminess (Reus and Kolus, 2007), have also been cited . the rate of both negative and positive trends can be substantially modified by the combine effort of both short term and long term climate drivers and long term trends in anthropogemic stressors (Cardoso  et al., 2004).

Change in SAV abundance can be abrupt, either as a linear response to an acute event or as a non-linear threshold effects in which a sudden shift occurs after gradually changing environmental conditions cross some critical threshold (Scheffer  et al., 2001; Van  der Heide  et al., 2009). Theory suggest that feedback processes, through which a plant, may facilitate threshold responses. For example, SAV beds attenuate wave energy and currents velocity, which causes suspended particles to sink, improves ambient water clarity and thus enhace plant growth (Ward  et al., 1994; Gruber and Kemp, 2010). SAV beds also decrease water column nutrient concentrations, thereby precluding the growth of phytoplankton and epiphytes and allowing more light to reach the leaf surface (Moore, 2004). Positive feedbacks helps to maintain a suitable environment despite changes in external conditions. However, beyond a critical threshold (e.g, a minimum light level needed for plant growth, feedback processes no longer buffer against disturbance and the systems suddenly shifts to a degraded state (Scheffer  et al., 1993). As conditions approach this threshold, resilence decrease and a small change in environmental conditions can drive the systems beyond its “tipping points”.

In some instances plant reestablishment in  bare sediment requires more stringent conditions than those needed to maintains an already established submerse plant bed can be extremely difficult. The initiation of positive and negative shift at different critical conditions can exist under the same set of environmental conditions e.g, turbid and clear water.

An abrupt increase in submerse plant abundance recently occurred in a broad shallow region in the upper shesapeake bay as susque hanna flats. SAV at “the flats” historically extolled by fisherman and water fowl enthusiast s prime wild life habitat, began to decline when nutrient leading to eutrophication intensified in the 1990 . (Bayley  et al., 1998; Kemps  et al., 2005). Following tropical storms Agness in 1992, submersed plants virtually disappeared for nearly two decades until early 2000 when they rapidly recolonized the entire region (50km²). Whereas an extreme flood events apparently triggered the demise of SAV at Susquehanna flats, the extended lack of recovery is puzzling because it appears that environmental conditions have generally satisfied the habitat requirement for SAV in oligohaline regions of Chesapeake Bay since water quality monitoring began in 1994 (i.e, April- October median light attenuations coefficient <2.0m^-1, total suspended solid and dissolved inorganic phosphorous concentrations <15mgL^-1 and 0.67molL^-1 respectively; Denilson  et al., 1993; Kemp  et al., 2004)