Here’s the abstract of a recent paper by Torben C. Rick and Jon M. Erlandson:

The development and spread of agriculture and pastoralism during the past 10,000 years is often seen as the tipping point when humans fundamentally changed our relationship with the natural world. Ancient hunter-gatherers also altered their environments, although the extent to which they did so remains hotly debated (1–3). Hunter-gatherers may have caused major alterations of terrestrial ecosystems, including the use of fire to enhance resource productivity and the translocation of various animals to new regions (3, 4). They are implicated in massive megafaunal extinctions in the Americas and Australia (2, 3). Recent archaeological research from coastal areas shows that they also substantially altered and enhanced marine ecosystems in other ways, some of which obscure the definition of the term “hunter-gatherer.”

And although the rest of the paper is behind a paywall, NPR offer some further discussion here.

Reference: Anthropology Coastal Exploitation     Torben C. Rick and Jon M. Erlandson (21 August 2009)     Science 325 (5943), 952. [DOI: 10.1126/science.1178539]     How did ancient hunter-gatherers influence coastal environments?