The source of the Mara is at the Napuiyapui swamp in the Mau forest of Kenya. The Mau forest nestles is Kenya's biggest forest block. It is a complex ecosystem that is the source of at least 12 rivers, draining westwards towards Lake Victoria and eastwards to Nakuru through Mau Narok, Lake Nakuru and the Mara-Serengeti ecosystem. It is also the single most important water catchments area in Western Kenya and a key source of water for Lake Victoria. The importance of the Mara river and its estuaries to Agriculture, forestry, water supply, makes it strategic to the economies and ecology of both Kenya and Tanzania and hence to the survival of the Serengeti. Most of the Maasai Mara National Reserve and about 10% of the Serengeti National Park are hosted in the Mara river basin. Together they make up a world wonder of biodiversity concentration. Proportionality aside, the internationally celebrated Wildebeest migrations would not take place without the existence and attractiveness of the Mara and Maasai-Mara to wildlife at certain times of the year. It is a time of breeding before dispersal starts again into the southern part of the ecosystem. Over the past 50 years the Mara River Basin has undergone land use changes that threaten the rich biodiversity of the ecosystem. The riverine forests of the Mara Basin are being cleared for charcoal and for crop farming. It is estimated that in the Amala sub-catchments area cultivation increased from under 20% in 1960 to over 51% in 1991 as the number of households increased by 13% in the same area. The once sparsely populated rangelands in the middle catchments around Mulot, Longisa, Norengore and Kobosom in Kenya are occupied by crop farmers who have displaced the traditional pastoralists. Pastoralism, in both the SNP and MMNR, has co-existed with wildlife for many years. However, the Maasai people are changing to a sedentary lifestyle that is increasing pressure on natural resources such as water, forest, wildlife, etc. Such human activities are, in principle, restricted in the ecosystem and what is now taking place is contrary to management goals of ensuring that the resources meet the needs of both the present and future generations. Subsistence farming has inundated the lower reaches of the Mara River Basin around Mosirori wetlands and beyond to the delta at Kirumi on Lake Victoria in Tanzania. The Serengeti is a trans-boundary ecosystem and as such it cannot belong to any one country in spite of the proportional share of its land area. Wildlife has no nationality and cannot therefore be confined within political or administrative boundaries. All they need is access to breeding and dispersal grounds and good management of wildlife sanctuaries ought to provide that needed space. The prudent approach to management is an ecosystems approach for the mutual benefit of conservation, the livelihoods of communities living close to the ecosystem and the economies of the two countries. The ecosystem is now being managed by Kenya and Tanzania separately and has therefore experienced a number of constraints to conservation. Investigations undertaken over many years show that the constraints include: (i) mismanagement of the resources of the ecosystem of which are many, both flora and fauna; (ii) human population pressure on the ecosystem; (iii) diversification of land use in the investment domain with tourism and the establishment of conservancies increasingly getting more attention to the detriment of biodiversity; (iv) Encroachment on the basin by human settlements, where small businesses are established to gain from tourism in support of their livelihoods; (v) Poaching that is threatening the animal population and with this threat a reduction in the number of species and diminishing returns from tourism and hunting. All these are antagonistic forces working against sustainability of the ecosystem, unless better management mechanisms are invoked.