community buildings have no water supply at all, and many households rely on polluted groundwater due to the shortage of treated water. Because of the shortage of fresh water, sanitation systems must use saltwater for flushing. The sanitation network on South Tarawa is performing very poorly, and a major project is underway to rehabilitate the system and improve sanitation and public hygiene. Coastal erosion The Ministry of Environment, Lands and Agricultural Development (MELAD) is involved in the replanting of mangroves in selected sites to help against coastal erosion; however, much more is required to protect many of the sites eroded on South Tarawa including islets that once were protected with mangrove and iron-wood (tengea) trees. It is unclear how much of the erosion being experienced on South Tarawa is due to sea-level rise and how much is due to human activities (such as building inappropriate seawalls and mining sand and gravel from the beaches and foreshores. Coastal erosion will accelerate in future, due to climate change related sea level rise. Land availability and overcrowding The land area of South Tarawa is officially recorded as or 15.76 square km. Much of this land is not available for use, including the water reserve and runway, the causeways, and a large area of reclaimed land at Temwaiku, the eastern corner of the atoll, which is too swampy and low-lying. If these areas are excluded, the land area of South Tarawa is only just over 1,000 hectares (10 square km or 2,500 acres) and the population density of 49 people per hectare or 4,905 per square km is almost equal to the density of London (5,100 people per km2) and twice the density of Sydney or Auckland. Multi-story buildings are very uncommon on South Tarawa. The high population is accommodated through large household sizes, with an average of 7.3 people per household, on small land plots. Most land is owned by the original families or kain Tarawa, although in the main centres of Betio, Bairiki and Bikenibeu there are large areas of land on long-term lease to the government. Without access to family lands or government housing, many South Tarawa residents have no choice but to become squatters; disputes over land are common. South Tarawa and especially Betio have high rates of respiratory infections, diarrhoea, and dysentery, all of which have been linked to overcrowding. Unsustainable development in South Tarawa is a concern to