Cardiff in making iron and later steel, brought to the sea by packhorse from Merthyr Tydfil. This was first achieved by the construction of a long canal from Merthyr (510 feet above sea-level) to the Taff Estuary at Cardiff. Eventually the Taff Vale Railway replaced the canal barges and massive marshalling yards sprang up as new docks were developed in Cardiff – all prompted by the soaring worldwide demand for coal from the South Wales valleys. At its peak, Cardiff's port area, known as Tiger Bay, became the busiest port in the world and – for some time – the world's
Cardiff Bay Wetlands Reserve are a transitional habitat between water and land; they provide an important habitat for many bird, fish, animal, and plant species. The Cardiff Bay Wetlands Reserve can be found near St David's Hotel close to Mermaid Quay. Prior to the construction of the Cardiff Bay Barrage, this area was made up of mudflats and salt marsh. The wetlands reserve was created in the new freshwater lake. The reserve is a biodiversity hot-spot within Cardiff Bay. The reedbed, a UK Biodiversity Action Plan habitat, along with other aquatic plants, are very productive vegetation. A number of bird species including reed buntings,