Peat bogs preserve pollen grains for centuries, giving scientists a record of ancient plant life.

The longer version

Waterlogged peat holds very little oxygen, and that lack of air slows the bacteria and fungi that normally decay organic matter. Pollen has an especially tough outer wall, so it survives long after the soft tissue around it has broken down.

Because each layer of peat builds on the one below, a core taken from a bog is effectively stacked in time. Counting grains from different depths shows which plants were common nearby as the centuries passed, and shifts in the mix track changes in climate and in the surrounding vegetation. Grain shape is often distinctive enough to identify the family, and sometimes the species, that produced it.

Where this entry sits

Plants and Trees gathers ordinary and surprising details about how green things live, from the tallest forest giants down to the moss on a garden wall. Expect notes on flowers, seeds, roots, leaves, fungi, and the quiet tricks plants use to spread and survive. The full list sits on the Plants and Trees page, where every entry is listed in order.