New Delhi, April 9 -- The rhythmic sounds of construction muffle the thud of farmers' hoes on a chilly morning in Rwanda 's capital, where new efforts aim to protect remaining agricultural land from relentless development in Africa's most densely populated country.

Eighty-four-year-old Mukarusini Purisikira had been a farmer before she fled the country to Congo during the 1994 Rwandan genocide against the Tutsis. Upon returning, she said, her family's land, which had stretched across the hills, had been taken away for construction. She gestured toward Kigali's high-rise buildings.

Now she grows maize and sweet potatoes on a piece of land the size of a small cottage, which she said is barely enough to feed her.

"It is all I have," she s...