1. What Is Succession, and Why Do Plants Take Turns?
Ecologists call the way the plants in a place change over time succession. A forest does not appear all at once. First come the plants that can live in open, sunny, difficult places. Later, other plants move in and the first ones fade away [1].
There are two starting points. In secondary succession, something such as a storm, a fire or a farmer's plow (a tool for turning over soil) has removed the plants, but soil is still there. Seeds and roots are often still in it, so a field left alone can turn into a young forest. In primary succession, the starting ground can be bare, with little or no soil or seed to grow from, like fresh lava or new volcanic ash. Most plants have to arrive from somewhere else. That is the harder case, and it is the one this note is about.
Volcanic islands are natural experiments for it. Scientists can watch the very first steps, because they know the ground was bare on a particular date.
2. Which Plants Arrive First on Brand-New Land?
It depends on what can survive the trip. Look at two islands on opposite sides of the world.
Surtsey is an island off the south coast of Iceland that rose out of the sea in a volcanic eruption in the 1960s. The Surtsey Research Society reports that the first flowering plant found there was sea rocket, a seashore plant, in 1965. Sea lyme grass, oyster plant and sea sandwort followed in the next few years. At first, none of them lasted through a winter. In 1968–69, sea sandwort became the first to survive one, and in 1971 it made its first seeds, which helped it spread. Mosses and lichens were also there early on, but the society gives no exact dates for them [2]. Sea rocket and sea sandwort grow on beaches, and the island was surrounded by sea, so plants that are used to salt and wind, with seeds that float or drift, had a head start.
Nishinoshima is a small volcanic island far out in the Pacific Ocean, part of Japan. A series of eruptions from 2013 to 2020 destroyed the plants that had been growing there. A landing in July 2025 found the first land plants since then. Near the coast, on volcanic gravel and ash, grew one kind of moss and two kinds of fern. Mosses and ferns do not make seeds. They spread by spores, which are tiny, light and can be carried over long distances. The research team described these as pioneer plants that were most likely carried to the island from elsewhere. Tomoyuki Nakano of Kyoto University said he was astonished that ferns appeared at the same time as the moss. The usual expectation is that lichens and mosses come first [3].
So the first arrivals are the plants that travel well and tolerate harsh ground: shore plants where seeds float, spore plants where wind carries them.
3. How Do the First Plants Help Later Plants Settle In?
The first plants do more than just sit there. They change the ground. Mount St. Helens in the US state of Washington shows this well. When it erupted in May 1980, it left an area called the pumice plain with, in the words of a Washington State University article, "no biological legacy": nothing alive survived [4].
Scientists found a single lupine plant there barely a year later. Lupine seeds are heavy and do not travel easily, so the wind probably carried it in. Insects likely arrived first, and as they died and decayed they added phosphorus to the ash. That helped the lupine take hold. Lupines also live with bacteria that take nitrogen out of the air, and when the plants die they leave nitrogen and rotting plant material in the ground [4]. Over the next decade, lupine patches spread widely, and other plants grew mostly beside them [4].
The same article adds a twist. Moths and caterpillars fed on the lupines, which helped keep the patches from spreading too fast [4]. Even on bare ash, plants, insects and soil start to affect one another.
Birds can do something similar. On Surtsey, a seagull colony settled in the 1980s. Inside the colony, where the birds enrich the soil, study plots held up to 10 plant species. Outside it in 2002, the plots held only 1 to 5 species, with less than 30% of the ground covered. The Society says the gulls were probably the main reason willows later spread on the island [2].
4. Why Do the First Trees Not Stay?
Once soil and shelter exist, trees can move in. Here a surprising rule shows up: the trees that arrive first often make a place where their own young cannot grow well.
Take a field in the northeastern United States after the farmer leaves. At first there are grasses, raspberries, and fast-growing, sun-loving trees such as aspen and paper birch. This stage lasts until the leaves overhead close up, which often takes 15 to 25 years. After that, the fast growers crowd one another, and some are shaded out and die [1].
The forest floor now gets little sunlight. Young sun-loving trees do not grow well in the shade. But seedlings of shade-tolerant trees, such as sugar maple, American beech and eastern hemlock, can wait in the dim light. When an old tree dies and opens a gap, they grow up to fill it. After several decades to more than a century, the forest is mostly shade-tolerant trees of many ages [1].
That is why succession happens at all. The earlier trees change the light, and the changed light favors different trees. How a forest changes over time differs from region to region with the climate. The example above comes from the northeastern United States, and forests elsewhere follow their own patterns.
5. Does a Forest Grow Back in a Straight Line?
The steps above are a handy outline, but real places do not follow them neatly. Surtsey is a good example: after the first years, few new plant species arrived between about 1975 and 1985, and the pace of change slowed. It picked up again later, in part because of the gull colony [2]. Nishinoshima, too, had only three plant species to show in 2025 [3]. A forest can also be set back. Storms, fire, insects and logging can push a stand to an earlier stage at any time [1].
So succession is better pictured as a general direction with pauses, setbacks and surprises than as a staircase.
6. Can People Plant a Forest That Finishes the Job Itself?
Meiji Jingu is a shrine in the middle of Tokyo, Japan, surrounded by a large forest. It looks ancient, but people planted it. The shrine says the forest covers 70 hectares and was planted around 1920 by about 110,000 volunteers. The trees were chosen for how they would look after 100 or 200 years, and the shrine says there has been no human intervention since. Fallen trees are left where they are, to return to the soil [5].
The land was not completely bare. According to nippon.com, only about 8 of the 70 hectares were wooded, and the rest was mostly fields and grassland. The plan was drawn up in four 50-year stages, ending in a mature forest of broadleaf evergreen trees that could renew itself from its own seeds. A survey in 2013 found that the forest had nearly completed the second stage, around 100 years in, and was on course for the third, around 150 years [6].
The planners used what they knew about succession to choose trees for different stages of the forest's growth. They did not try to plant a finished forest. They planted a start and trusted time to do the rest. Whether the forest will fully reach the plan's last stage is something only later surveys can show.
Watch Succession Happen Near You
You do not need a volcano. Find a patch of ground where plants are just starting, such as the edge of a parking lot, a gravel strip, or a cracked pavement corner. Pick one spot and sketch which plants are growing there. Go back a month later and look again. Which ones grew, which ones disappeared, and what has appeared that was not there before? Stay on the path or sidewalk, do not pick the plants or step into private land, and go with an adult if the place is not part of your own yard.
To read more, the Surtsey Research Society's pages [2] and Washington State University's article on Mount St. Helens [4] are good places to begin.