A new study has found that as farming spread across ancient Europe, plant diversity rose rather than fell. Researchers reading pollen buried in Swiss lake mud tracked the pattern over roughly 7,000 years, and found the land grew richer in species as agriculture expanded. The reversal hints that today’s losses may not be permanent, because diversity rebounded each time earlier societies returned to varied, small-scale farming. The record comes from three lakes on the Swiss Plateau, a fertile lowland north of the Alps that has been farmed for thousands of years. He sampled the cores in thin slices, dissolved away everything but the pollen, and counted 500 grains under a microscope for each one, identifying the plants they came from. Across the three sites he worked through more than 2,000 samples, anchored in time by over 220 radiocarbon dates and, in places, by sediment layers that each formed in a single year.