Assisted Migration

What is assisted migration?

Forests have always moved. As climates shifted after ice ages, tree species advanced and retreated across continents — but slowly, over thousands of years, as seeds spread a little further with each generation. Today the climate is changing within decades, and many trees simply cannot keep up. A species perfectly suited to a place two hundred years from now may have no way to reach it in time.

Assisted migration is the deliberate human help that bridges that gap: moving species, or seed collected from better-adapted populations, to areas where they are expected to thrive as conditions change. It ranges from the modest — sourcing seed of a local species from its hotter, drier edge — to the ambitious — establishing a species beyond its current range.

It is a subject of serious scientific discussion, because moving living things carries risks as well as promise. Done carelessly it could introduce a species that becomes invasive; done thoughtfully it may keep a forest alive that would otherwise decline.

How Terra Humana understands it

Terra Humana approaches assisted migration with humility and a strong bias toward caution. Our first commitment is to native Mediterranean species and to the genetic diversity within them — including seed from the driest, most heat-tested populations, which may carry the resilience the future demands.

Where we look further afield, it is only toward trees from comparable climates and with a long, safe history in the region, and never toward anything that could crowd out native life. The guiding idea is the same one that runs through all our work: to assist natural processes, not to override them. Assisted migration, used well, is a way of helping a forest do what it would do on its own if only it had the time.

Assisted migration in practice

At Sa Medada, near Jerzu, the practical expression of these ideas is careful seed sourcing and close observation. Terra Humana pays attention to where the seed of a species comes from, not only which species it is — because a holm oak grown from drought-hardened parents may fare very differently from one grown from a wetter site.

This is patient, watchful work, and deliberately modest in its ambitions. By recording how different species and seed origins cope with the real conditions at Sa Medada, Terra Humana builds honest, local knowledge about how Mediterranean forests can be helped to endure a warming world.