Agroecology could be defined as the science of sustainable agriculture. Despite the efforts of the "green revolution" (that aimed at insuring food security on a global scale in the 1960s), famine has not been eradicated from the planet and the availability of high technological tools (e.g.: chemicals GMO's) may not insure the long term sustenance of farming systems. The principles of food production may be easily generalizable however, the ecological diversity of geographic contexts in which agriculture takes place demand (necessarily) an adaptation of approaches to food production. The indigenous knowledge of growing food is a valuable resource in agroecology and the compelling need of saving germplasm from extirpation depends also in the maintenance of a specific culture of 'practicing agriculture'.
I am linking to a paper I co-authored in 2008 that hopefully will assist you to better understand my thoughts and vision to achieve sustainability from an agricultural perspective.