The nature reserve “The big and the white moor” (Fig. 1) is located in the Lower Saxony, in the district of Rotenburg (Wümme). Even though it used to be almost dry, it has been recovered and naturalised due to the drainages made for agricultural purposes. Today, it is among the best preserved raised bogs in the North-West Germany.
Raised bogs are acidic, wet habitats, poor in mineral nutrients, populated by plants adapted to live in such extreme conditions (Fig. 2). In north Germany they can develop only under ideal climate conditions – wet with a balanced distribution of precipitations over the year.
The development of the bog started around 4000 years ago. At first a flat bog developed thanks to sand deposition and accumulation of water. Slow acidification of the trapped water allowed the accumulation of partially decomposed plant material under low oxygen levels, which developed into peatland. At this stage, the inhabiting plants were sedges, rushes, deergrasses, Phragmites and alders. In the transition stage, other plant species folowed – bushes, trees, peat mosses and cotton-grasses. The rised bog developed very slowly, in a period of many centuries, along with strong rainfalls.
The peat, accumulating over time, traps CO2 gasses by reducing their amount in the atmosphere. Therefore bogs are important for the climate and by protecting them, we protect the climate.
About 60% of plants of the german bogs are threatened. Among them, the heather (Calluna vulgaris, Fig. 3), and the cross-leaved heath (Erica tetralix, Fig. 4) are very common. Both are low growing perennial shrubs, easily found in the heathland and moorland, growing in acidic soils in sunny or partially shady places, adapted to live in low nutrient conditions. Cross-leaved heath is particularly vulnerable because the increased drainage creates drier conditions, where it is quickly replaced by the moor grass Molinia. However, gradual naturalisation is essential for the survival of this plant in this protected area.
Increased drainage permits the growth of Molinia, birch and pine trees (Fig. 5). As the forest develops, it absorbs more water so that the typical conditions for bog plants survival are quickly lost.
However, last summer (2016) was extremely hot and dry, the precipitations were not well distributed and the temperatures were well above the average. While in July everything looked fine, in September the picture was a bit different. The pond where the frog from the Fig. 5 has been found become almost dry in September (Fig. 8 and 9), even the blueberries were flaccid or dry. The conditions worsened in the next weeks, with temperatures above 30°C and no rain.
I like to think that it was just an exceptional year and that it will only rarely happen to have such extreme conditions in Northern Europe, but I´m not that optimistic for the future of this peculiar biotope.
Photos by Ingrid Ugussi Vukman