Ecology Pre-European Colonization
After the glaciers receded about 12,000 years ago, the land around Carmans River came to life rapidly, as both plants and animals moved to take advantage of the new ground. It is likely that the first vegetation in the area was tundra and spruce-fir, as it was still very cold and wet. This initial period was interrupted by a few thousand years of warmer and drier climate, which probably saw the introduction of pitch pine, oaks, and other drought and poor soil tolerant vegetation such as heath. The return to “normal” brought a trend toward pitch pine, tree oak, dwarf pine, and scrub oak. Pitch pine, in particular, has evolved to make use of fire in its life cycle: the pine cones can only be opened by extreme heat.
The Native Americans of the Late Woodland era actively managed forests in order to burn off underbrush and deadwood that made hunting difficult, to improve soil fertility for crops, and also to promote particular kinds of growth that were good for game species. However, there is considerable uncertainty today about the extent and distribution of pre-European species. This is because the land has been used so intensively since then that several waves of succession may have taken place and native succession species may have gown and been replaced.

Thus what we might see today as “natural” does not necessarily equal “original.” (For example, one tree from this time that barely survives is the American chestnut, due to a horrific blight.)
Prior to European arrival, the Native Americans in the area of Carmans River “relied on a broad-based hunter-gatherer subsistence strategy that varied among coastal, riverine and upland areas,” according to Glenn Motzkin and David R. Foster (pdf). The fish and shellfish of the ocean, bay, and river would have been supplemented with game mammals and birds as well as nuts, berries, edible plants, and more processed foods such as acorn flour and cattail rootstock flour. They would also have had gardens in season, growing things like corn, beans, and squash.
Unkechaug Nation
The Unkechaug community or band who lived on the banks of Carmans River were Delaware Algonquian speakers most likely within the dialect associated with the Mohegan tribe, which also included the Montauk and the Shinnecock. Note: “Algonquian” is a language group; “Algonquin” is a specific language in that group spoken by the Algonquin people of Quebec and Ontario. “Poospatuck” is the place name of the area (meaning “where the waters meet”) that is the reservation on which many members of the Unkechaug now live.
Historian John Strong explains in the Hudson Valley Review: “Tribes are much larger than bands and are unified by age and gender associations that cross lineage and clan affiliations. One crucial difference between a band and a tribe is that tribal societies are ideological groups that have a distinctive name that is usually invested with deeply felt emotional symbolism, while bands have an informal collective identity rooted in clan or kinship relations.”
Because Long Island’s groups did not have either large-scale agriculture or sedentary settlements until after Europeans came, it seems most correct to refer to the societies as bands, although this term does not do justice to the dynamic fluidity of villages and family groups that would fuse and separate according to the season. More rigid structures were forced as a result of contact with the Dutch and English, who insisted on stricter governance of both behavior and land. However, as Strong also notes, this allowed these groups to retain their identities amid the onslaught of immigrants.
While there are no extant images of their life, there are some that come fairly close. This image is of an Algonquian village in North Carolina after Europeans arrived. John White, the man who painted it,

was a Virginia colonial governor in Elizabethan times. But he is more famous as a watercolorist of note. According to Benjamin Breen in The Public Domain Review, “White … had a remarkable ability for “zooming out” from a scene to create an imagined isometric perspective. His painting of an Algonquian village stands out as one of the most detailed depictions of indigenous American village life to survive from the sixteenth century. As the detail of the dancing circle in the lower right of this image suggests, White seems to have had a particular interest in Algonquian religious ceremonies.”