Bogs grow so slowly that losing one can take millennia to undo
In a bog, plants grow sluggishly, but they rot even more slowly, because the waterlogged, acidic ground holds almost no oxygen. Dead moss piles up year after year as peat, sometimes many metres deep. That stubborn refusal to decay makes bogs vast stores of carbon and turns them into something like slow-motion archives.
A bog is a wetland that builds peat, usually from sphagnum moss. What sets it apart from its cousin the fen is where the water comes from. A bog is fed mainly by rain, which carries almost no dissolved minerals such as calcium to neutralise acidity, so it stays strongly acidic and poor in nutrients. Fens draw on mineral-rich groundwater and can range from slightly acidic to slightly alkaline. Water draining from a bog runs brown, stained by tannins from the peat.
Life there is specialised. Sundews and pitcher plants make up for scarce nutrients by trapping insects; orchids lean on fungal partners; bog myrtle hosts root nodules that fix nitrogen. Caribou, moose and beavers use bogs, as do Siberian cranes, and Ireland's only known reptile, the viviparous lizard, lives in its bogland. England's bogs shelter a yellow insect called the hairy canary fly. On a quaking bog, a floating mat of moss about half a metre thick rests on water, so a footstep can send ripples outward and make trees sway.
Bogs form in several ways. A lake can gradually fill with silt and peat, passing through marsh and fen stages until its centre rises beyond the reach of groundwater and becomes rain-fed, eventually swelling into a raised dome a few metres high. Where rain falls on more than about 235 days a year, peat can drape whole hillsides as blanket bog, as across Ireland, Scotland and Norway. The world's largest wetland is the peat bog of the Western Siberian Lowlands, exceeding a million square kilometres, and a 2014 expedition from Itanga in the Republic of the Congo found one reportedly as big as England.
Peat has long been dried and burned for heat, supplying over a fifth of home heating in Ireland, while Russia exports more than 90 million tonnes of it a year. Drainage, cutting and warming now threaten these ecosystems. Arctic and sub-Arctic bogs are warming at 0.6 °C per decade, double the global average, and as they dry, stored carbon escapes as greenhouse gas.
Source: Bog
