FWS Focus



The southern Appalachians are home to the highest peaks east of the Mississippi River. These peaks are home to forests dominated by Fraser fir and red spruce, remnants of the last ice age. It’s a community more akin to Canada than anything across the southeastern United States. Bryophytes such as mosses and liverworts are common on this moist, cool forest floor, and bryophyte mats that grow on rocks and are of just the right moisture and thickness, are home to the endangered spruce-fir moss spider.

Not a high-profile nor high-charisma animal, the spruce-fir moss spider is about the size of a pencil eraser. Its entire known global distribution consists of less than 25 mountain tops, spread across six southern Appalachian high-elevation areas: the Virginia Balsam Mountains in Virginia, Grandfather Mountain in North Carolina, Roan Mountain in North Carolina and Tennessee, Black Mountains in North Carolina, Plott Balsam Mountains in North Carolina and Great Smoky Mountains in North Carolina and Tennessee.

Although many of the places where the spider lives are protected from the habitat degradation or conversion that can come from poorly managed development or resource extraction, the spider faces challenges based on its limited, disjunct habitat. The six high-elevation areas where it lives are considered sky islands, with a plant community dependent on the climate and landscape features only found at these high elevations. Functionally these areas are islands that are separated by spans of lower-elevation forest types which are unusable by the spider.

The high-elevation conifer forests that the spider depends on were dealt a blow around the turn of the 20th century, when the area experienced industrial-scale logging, followed by catastrophic wildlife fires. The result was significant shrinkage in the amount of high-elevation conifer forest. In recent decades these areas have suffered from acid precipitation and the arrival of an invasive insect, the Balsam woolly adelgid, which attacks and kills Fraser firs. Both of these open up the forest canopy, which contributes to the drying of moist forest floor on which the spider depends. As these are isolated, cold-climate habitats, today their future is called into question by the threat of climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change

One of the most significant things that we are doing to help conserve this spider is to play an active, leadership role in the Southern Appalachian Spruce Restoration Initiative, a multi-organizational partnership to that aims to expand red spruce forests on these sky islands. Doing so provides more habitat for the spider, as well as improved habitat connectivity as patches of conifer forest within a sky island are connected.

Scientific Name

Microhexura montivaga
Common Name
Spruce-fir moss spider
FWS Category

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