The environmental conditions that dictate what grows in the backyard garden also determine what grows in the Tamar River estuary. The quality and type of ground, seasonal rain and temperature, nutrient availability, exposure to sunlight, and competition between plants and animals determine what lives where in the Tamar. The Tamar River estuary is a drowned river valley, with rock, sand and silt substrates each supporting different plants and animals. Dry summers and wet winters affect temperature, salinity and light levels, while nutrients coming off the land are used for growth. Winter conditions are harsh in the Tamar, with only the hardiest species surviving throughout the year (perennials), while summer provides an opportunity for growth and the chance for annual species to thrive.
Just like a garden in full bloom attracts a range of insects, birds and animals (both wanted and unwanted), the Tamar supports a similar diversity of animals. Where the blue-tongued lizard can help keep snails in check, the sea star forages for marine snails to feed on; and just as birds visit a garden to forage for insects, seahorses feed on small insect-like animals.