Background
Saltmarsh sparrows nest exclusively in salt marshes¹.  The breeding range for this species is limited to a narrow band of tidal marsh that extends from Maine to Virginia, with up to half of the global population estimated to breed in southern New England².  Females nest close to the ground in areas that are prone to flooding³ and their reproductive cycle is adapted to the ebbs and flows of the tide^4,5.  Their nesting is synchronized to the tidal cycle and is timed to occur between extreme tide events to avoid flooding of nests^4,5.  Despite this, flooding is still the major source of nest losses, accounting for 60% of failures².

Climate Impacts
Climate change is expected to result in rising sea levels due to melting of glacial ice and thermal expansion of water (water expands and has more volume when warmed)⁶.  Sea levels have been rising at an accelerated rate for at least the past 50 years in New England, exceeding average global rates^7,8.  In addition, there is an expected increase in the frequency of severe storms along with higher storm surges, which is likely to result in increased flooding of tidal areas during storms^9,10.  The northeast in particular has experienced approximately one foot of sea-level rise since 1900, and is projected to experience anywhere between 1.5 to 6 feet of additional sea-level rise over the next century^8,11. 

Because saltmarsh sparrows have developed a finely tuned reproductive strategy to cope with a flood prone environment, there is concern that the above changes could have a large impact on this species through increased nest failure^2,3.  Sparrow nests appear to be extremely vulnerable to even slight increases in sea level, leading some to suggest a bleak future for this species². For instance, the maximum tide height for successful nests without being flooded was just 6 cm higher on average than failed nests². In addition to the direct effects of nest flooding, changes in sea level may result in changes to the distribution and character of coastal wetlands⁷, which could have additional impacts on saltmarsh sparrows.  Modeling studies conducted by the University of Massachusetts that incorporate landscape characteristics and climate change, predict a 41% reduction in the capability of the northeast landscape to support saltmarsh sparrow populations by 2080¹². A study conducted for the Chesapeake Bay suggested that saltmarsh sparrows could lose up to 100% of their population with a 3.3-6.6 ft rise in sea levels by 2100¹³.