Fauna
Sainte Croix Island is not only covered with trees, flowers, grass and shrubs. Many animals live in the Quoddy region but a few have chosen the island as their habitat.

To learn more about the local fauna, it is necessary to observe the saline waters of the Sainte Croix River, the forest and grassy plains of the Quoddy region. Sometimes animals visit the island, perching or nesting in its trees, etc. Recently, a study has revealed that some birds inhabit the Sainte Croix Island such as spotted sandpiper, black-capped chickadee, song sparrow, common loon, veery, osprey, crow and bald eagle. More than 200 species of birds are found in the region and occasionally visit the island.

The mammals living in the Quoddy area are as numerous as their winged friends. The mixture of forest and plain is a perfect habitat for mammals and the rivers constitute a good source of food. In the grassy plain and in the surroundings of the forest, one finds small mammals such as red and grey squirrels, raccoons, woodchucks, chipmunks, deer mice, several species of bats and a large variety of rodents and insectivores. Unfortunately, bears, moose, deer, and wolves deserted the region a long time ago, leaving it to small animals eating grass, wild berries, fish, insects, etc. There is no record of amphibians or reptiles ever living on the island.

The region called Quoddy is composed of an incredible hydrographic basin, including the Sainte Croix River estuary, the Bay of Fundy and the Passamaquoddy Bay, dumping its waters into the Atlantic Ocean. Its shallow or tidal waters with rocky or sandy bottoms are excellent habitats for mussels and clams. Other animals can also be found in these waters or region. The Quoddy area is a real paradise for amateur or professional fishing: alewife, pollock, haddock, salmon, cod, tomcod, smelt, halibut, mackerel, hake, pout, herring, and shad.

Other marine mammals live in the Saint Croix River estuary and the Passamaquoddy Bay, including harbor seals or harbor porpoises which often sunbathe on the shores of the island or the mainland. Sometimes whales visit the Bay of Fundy. From July to September, one might see finback or minke whales swimming in the bay. Unfortunately, over hunting has drastically reduced the number of whales visiting the region.

Flora
Although Saint Croix Island was not suitable for colonization, several species of plants and animals are able to thrive in the Quoddy region. The composition of its ecosystem has been modified quite a bit over the last dozen millennia. From the glacial time to the climatic warming of our planet, the vegetation has changed from tundra to spruce forest first, then to coastal forest. Colonization and intensive logging have destroyed a part of the mixed forest (softwood and hardwood trees): settlers loved the quality and solidity of pine and maple woods.

Today, the Quoddy forest is composed of red spruce, yellow birch, mountain ash and maple. The coastal forest changes to a mixed forest as soon as we enter the inland areas. There, one can find a mixture of white and black spruce, balsam fir, and tamarack. In the uplands of Quoddy region, maple, birch, beech, spruce, fir, pine, and hemlock can be found everywhere. On the littoral zone, a diversity of plants covers and grows on the landscape.

On Sainte Croix Island's interior plateau, patches of trees and herbaceous and woody plants create a mixed shrub forest. American beech, white cedar, birch, wild rose and raspberry color and perfume the area. The shore section of the mainland is more like a transition zone between the prairies and the forest, fairly extensive in area, characterized by tall herbaceous vegetation, scattered large trees, and scrub. White spruce, balsam fir, white pine, red oak and paper birch grow in this part of the island. The mainland is less wooded; tall herbaceous, grass and shrubs cover this landscape. Nevertheless, visitors are always enchanted by the colorful diversity of the vegetation: wild rose, raspberry bush, silverrod, alder and cherry.

It is important to protect the landscape of this region and to stabilize the steep banks from erosion due to wind and water. In order to stop this plague from devastating the region, the National Park Service has planned to plant trees on the Sainte Croix Island and its surroundings. The reforestation might be beneficial to herbaceous area: it will enrich the soil with minerals needed by the vegetation.