Human Impact

            Humans have impacted Sequoia forests in a variety of ways. From 1800 to 1950, logging devastated the region. During this time period, 34% of the original range of sequoia timber was lost to extraction. Though preservation efforts put an end to this destruction, humans continue to hurt natural sequoia habitats. Walking or driving over tree roots can damage them, and road and building construction in the region decimates the soil. Clearing land can also change the soil moisture in the region, negatively affecting sequoia habitats. "Modification of landforms causes water runoff from rainstorms and snowmelt to concentrate and form gullies, causing soil erosion." 

            Furthermore, wetland and stream habitats are negatively affected by leaking sewage. Runoff from nearby parking lots depletes soil of organic matter and alters its structure, devastating the sequoia populations and surrounding habitats. Fire prevention strategies also focus on removing the natural duff layer from the forest surface. This absence reduces the ability of surface soils to hold water and maintain the aeration necessary for root health. The corresponding loss of organically rich topsoil causes big problems for sequoia forests.

            Fire suppression is perhaps the most dangerous issue to sequoia populations. The health of the trees requires frequent, low-intensity fires to burn and clear undergrowth in order to allow new sequoia seedlings to take root. Fire prevention strategies prevent sequoias from regenerating successfully, while allowing competitor species to proliferate. Human intervention also causes dead leaves and branches to build up which leads to larger and more destructive fires. The below graph shows the actual versus desired levels of surface fuel. 

As you can see, surface fuels build up, drastically increasing the severity of fires when they do occur. In addition, far more fires are caused by humans than natural causes. As the below graph depicts, human-caused fires have burned approximately 250,000 acres more than lightening-caused ones. 

            Today, the giant sequoia is recognized as a national treasure and as much as 90% of the population is protected. The best-known groves are found in Yosemite, Sequoia, and Kings Canyon National Parks, which attract tourists from throughout the world. "33 of the 75 natural groves of sequoias are under National Park jurisdiction," and these groves occupy approximately 11, 223 acres of giant sequoia. The National Park Service is dedicated to protecting the groves and individual trees in its care, and intensive forest fire protection provisions exist for all groves in public ownership. In order to recreate historic conditions, the National Park Service now practices controlled burning in order to proliferate the region’s sequoia populations. Still, significant research needs to be done to determine the appropriate number and length of burn days. As you can see from the graphs below, the number of burn days annually has decreased since 1973. Burn days are typically scheduled when the fuel moisture criteria is met. This is because there cannot be a controlled burn on a day in which the forests are extremely dry or else the fire will become too large and too destructive. Therefore, the decreasing amount of days on which this moisture criteria is met makes it difficult to implement controlled burns successfully without them getting out of hand. 

While the area is classified as vulnerable on the International Union for Conservation of Nature Red List 2007, the human impact on giant sequoia groves is luckily not disastrous. The protection and conservation of groves of sequoias has ensured this, but humans still have the capacity to destroy these forests due to the above impacts. If logging, road and building construction, and fire prevention continue to occur, human impact will remain mostly bad, if not ugly. Therefore, it is vital to continue to devise plans for preserving these giant sequoias for the esthetic and scientific purposes we as humans value them for.