A bog is a freshwater wetland of soft, spongy ground consisting mainly of partially decayed plant matter called peat. Bogs are generally found in cool, northern climates. They often develop in poorly draining lake basins created by glaciers during the most recent ice age.

The world's largest wetland is a series of bogs in the Siberia region of Russia. The Western Siberian Lowlands cover more than a million square kilometers (386,102 square miles).

There are several distinct types of bog habitats. Blanket bogs develop in highland areas with significant rainfall: the bog "blankets" an entire area, including hills and valleys. Cataract bogs are ecosystems that feature a permanent freshwater stream. Quaking bogs develop over a lake or pond, with bog mats (thick layers of vegetation) about a meter (3 feet) thick on top. Quaking bogs bounce when people or animals walk on them, giving them their name. Raised bogs are vaguely dome-shaped, as decaying vegetation accumulates in the center. String bogs have a varied landscape, with low-lying "islands" interrupting the saturated bog ecosystem. Valley bogs develop in shallow valleys.

All bogs take hundreds or thousands of years to develop. A bog is formed when a lake slowly fills with plant debris. Sphagnum moss, as well as other plants, grow out from the lake's edge. The vegetation eventually covers the lake's entire surface.

Bogs can also form when the sphagnum moss covers dry land and prevents precipitation from evaporating. These bogs are called ombrotrophic bogs.

Plants decay slowly in bogs, because flooding prevents a healthy flow of oxygen from the atmosphere. Bog soils are oxygen- and nutrient-poor, and are much more acidic than other soils.

Eventually, watery bogs become choked with living and decaying plants. These slowly decaying plants become the main components of the bog's soggy soil, called histosol.

Fungi and low-lying shrubs, such as heather, grow in histosol. Heather can grow directly on sphagnum moss. In fact, bogs are often called "heaths" after the abundance of heather that blankets them.

Peatlands

Thick, spongy layers of histosol eventually form peat. Peat is a fossil fuel that is the first stage in the long process of plant material turning into coal. Ancient bog plants, mostly sphagnum moss, are the fossils in peat.

People have harvested peat for thousands of years. It is a source of energy for heating, insulation, and electricity throughout northern Europe. Thousands of bogs throughout Ireland, Scotland, Scandinavia, and Russia have been drained for peat excavation.

Thick blocks of peat are cut and allowed to dry. The blocks are then burned. In some places, such as Ireland, peat is an industrial fuel for electricity and heating. In places like Scotland or Scandinavia, individuals or communities harvest peat for use as a cooking fuel.

Tropical peatlands, located mostly in southeast Asia, are sources of valuable timber. They are also popular sites to drain for development.

Dried peat is also used in agriculture. Peat, sometimes called "peat moss," increases soil's ability to retain water.

Bog Ecology

Bogs are ecologically important because they absorb great amounts of precipitation. They prevent flooding and absorb runoff. Sphagnum moss, reeds, sedges, and heather are common bog plants.

Bogs that receive all their water from precipitation (not lakes, glaciers or groundwater) are ombrotrophic. Ombrotrophic bogs have very few nutrients, making it difficult for many common plants to survive. Carnivorous plants have adapted to ombrotrophic environments by not absorbing nutrients from the surrounding water, but from insect prey. These carnivorous plants, such as sundews and pitcher plants, trap insects and dissolve them for nutrients.

Bogs that are fed by lake basins and other water sources have even more biodiversity. Plants that grow in these bogs include cranberries, blueberries, and huckleberries.

Insects thrive in muddy bogs and consume plants, fungi, and pollen. Many bog insects, such as the hairy canary fly, do not live in any other ecosystem. The hairy canary fly (named because of its yellow coloring) is an indicator species for European bogs.

Bog plants and insects support a wide variety of other organisms. Amphibians, such as frogs, salamanders, and newts, thrive in insect-rich bogs. Threatened species of cranes nest in bogs and peatlands in North America and Siberia. Raccoons are one of the largest mammals able to make their homes in bogs, although moose, beaver, and river otters often visit bogs to feed or find shelter.

Climate Change

Peat bogs are carbon sinks, meaning they store enormous amounts of carbon, in a process called carbon sequestration. Carbon sequestration is a process where carbon dioxide is captured and removed from the atmosphere. The carbon is stored, or sequestered, in a natural or artificial facility.

Plants are a major source of carbon in the environment. By creating new bogs, millions of tons of carbon are sequestered. The world's peat bogs sequester more than 200 billion tons of carbon. Much of this carbon is trapped in semi-frozen tundra and boreal forests in Scandinavia and Siberia.

Carbon dioxide is a major greenhouse gas. Carbon emissions contribute to global warming, the current period of climate change on Earth. As the Siberian tundra thaws, millions of tons of carbon and other greenhouse gases stored in frozen bogs, such as methane, are released into the atmosphere.

Carbon is also emitted as nations destroy bogs for development and peat extraction. Peat ignites very quickly and burns very slowly. Peat fires can smolder for days without much notice. Fires in Burns Bog, British Colombia, Canada, burn underground for months. In 1997, peat and forest fires in rural Indonesia released about 1,000 kilograms (2,205 pounds) of carbon into the atmosphere.

Draining a bog for development or peat extraction destroys the ecosystem. Unlike other wetlands, bogs take thousands of years to develop and hundreds of years to recover. Extensive peat extraction in England, for example, has permanently destroyed more than 75% of the country's bogs.

Because bogs are such delicate and fragile ecosystems, conservation efforts mostly focus on government protection and preservation. Today, local and national restrictions prevent agricultural or industrial development on bogs throughout England.

Bog restoration projects are more rare than regulations on development. There are two major types of bog restoration projects. The first involves the removal or partial removal of peat from the bog, while the second maintains a crust of hard peat. In both restoration projects, water saturates the area, and sphagnum moss and other bog plants are introduced. Often, chemicals are added to the restored bogs to increase their acidity and create histosol.

Bogs and People

For thousands of years, people have regarded bogs as spiritual or haunted places. Their spongy and sometimes slow-burning soil created mysteries for Bronze Age and Iron Age societies.

Perhaps the most lasting testament to ancient reverence for bogs are bog bodies. Bog bodies are the remains of people who died in bogs or were placed there after their deaths. More than a thousand bog bodies have been found throughout northern Europe.

Archaeologists and anthropologists have studied bog bodies for clues to ancient societies' culture and traditons. They have discovered that most bodies, which range from children to the elderly, did not die of natural causes. Some retain nooses around their necks, others have arrows lodged in their chests. These ancient people may have been murdered, but were probably victims of ritual sacrifices.

The low-oxygen, acidic soil of bogs preserve bog bodies remarkably well. Remains more than a thousand years old retain their skin, internal organs, and even beard stubble. Unique hairstyles and tattoos are clearly visible.

The poor soil quality and lack of drainage have made bogs unpopular places for settlement. The rich biodiversity and other natural resources, however, have made rural and urban areas around bogs popular places for community development. The bogs of Teufelsmoor, Germany, ring the major city of Bremen. The nature reserve of Moseley Bog is part of the Moseley suburb of Birmingham, England.