(A) Climates

• Temperature and rainfall are involved in mangrove distribution.
• Mangroves are restricted in tropical and temperate coastlines. The low temperature of winter in HK may restrict the spread of mangrove since some species cannot ripen below certain temperature.
• Rainfall can determine sediment loads and salinity concentration.

(B) Rates of sedimentation

• Mangrove communities develop best where abundant silt is brought down by rivers and is allowed to accumulate by the slowing down of the river currents as it nears the marine environment.

(C) Salinity

• Mangroves grow best when the water is saline.
• Fresh water can maintain an optimum salinity balance and supply additional inorganic nutrients that are present in terrestrial run-off.
• Mangroves dominate the saline coastal zones because they have a higher tolerance for salt than their potential competitor plant species.

(D) Physiography

• A low gradient and high tidal range of shorelines provide large areas for the deposition of sediment and thus provide a suitable substrate for colonization.
• A steep gradient of shorelines cannot develop large areas of sediment and hence hinders the establishment of mangrove vegetation or allows only fringe communities to develop.