Urban expansion
The largest risk is the swallowing up of arable land. cannibalism.
Arable land is limited and, apart from the oceans, it is the only source of food production. Of this planets 148 million square kilometres of land, approximately 31 million are arable; however, arable land is being lost at the rate of over 100,000 km per year as a result of urban sprawl and drought. If this is seen against a growing population, it becomes clear that arable land per head of the worlds population is reducing at an alarming rate. While it was a mere 0.51 ha per person in the year 2000, it will become about 0.34 ha per caput in 2050, a reduction of 33 per cent or one third. If scientific predictions of rising oceanic water levels resulting from the melting of Arctic and Antarctic ice eventuate, then available arable land will shrink even more as a result of flooded deltas and low-lying islands being submerged.
