Christmas Island

Over the eons, physical erosion of the soft limestone surface of Christmas Island has enabled soil to form. In addition, the large colonies of seabirds living and nesting on Christmas Island over the centuries has enabled a thick blanket of phosphate-rich soil built up. The deepest soils occur on the central plateau and the upper terraces. The distribution of plants can be correlated to soil depth and moisture, exposure and distance from the sea. The coastal zone is generally saline with thin soils. The zone immediately behind this is also a harsh habitat for most plants, especially where it faces the prevailing south-easterly winds. Pandanus and salt bush (Scaevola taccada) are typical of places exposed to salt spray. Further inland where the environment becomes more sheltered and thus soil layers thicker, lush rainforest establishes.