If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Ecological succession

Ecological succession, a dynamic process involving gradual changes in biological communities over time, encompasses two main types: primary succession, where life gradually colonizes a new habitat, and secondary succession, triggered by a disaster that disrupts an existing community, instigating shifts in species composition. Created by Sal Khan.

Want to join the conversation?

  • duskpin tree style avatar for user Sarah Joy
    Would a forest recovering from a harsh winter in the springtime be considered secondary succession? Or really, could any forest in the spring recovering from any winter, just in general, be considered secondary succession? Does it always have to occur only after some sort of disaster, like a forest fire or a spread of a disease? I'm just curious.
    (18 votes)
    Default Khan Academy avatar avatar for user
    • winston baby style avatar for user Ivana - Science trainee
      Great question!

      Secondary succession is when species recolonize the habitat.

      I do not think that during winter species are wiped off the forest. they do change their behavior action and plant are hidden under the snow, but it does not mean they disappear.

      If you consider swallow migration to South and then returning to North in the spring, only in that case your definition can apply.

      Those are migrations and cyclic changes that happen every year regularly (under just one year span) so I am not sure whether we can call it secondary succession.

      I'd like Ecologists to jump in here and help me. This is not my expertise so probably this answer is full of holes.
      (12 votes)
  • starky tree style avatar for user imamulhaq
    There is a big controlled fire near my house to protect pine bush trees from invasive species. Then more native plants start appearing. is this ecological succession?
    (9 votes)
    Default Khan Academy avatar avatar for user
    • leafers sapling style avatar for user ysobel.gallo
      Yes, it is secondary succession, because the native plants come back from their deep roots or seeds that survived. It is like the example in the video about the forest fire, where the fire makes room for new things. In your example, the fire is getting rid of the invasive species and making more room for the native plants that come back.
      (7 votes)
  • duskpin sapling style avatar for user emmadumatrait21
    So are there other things that cause a secondary succession. I know that a natural disaster has to take place along with the previous presence of life, but is there another key element to this occurring?

    (8 votes)
    Default Khan Academy avatar avatar for user
    • starky sapling style avatar for user K.L.F
      Good question, I’m actually not too sure on this one, but I think one other way for secondary succession to happen is when a habitat is abandoned and there starts to be less life in that area because maybe they found a nearby lace that is more suitable for living, then other species start to live in the abandoned habitat and life starts again there, that is the only other way I can think of at least, but this way is probably unlikely. Hope this helps :)
      (3 votes)
  • duskpin ultimate style avatar for user Deadpool
    would lava turn to rock when it hits cold water
    (6 votes)
    Default Khan Academy avatar avatar for user
  • blobby purple style avatar for user hpradana8
    what is the different between plant succession and animal or zoological succession ? are they influence each other ? or the pioneer species are always plant ??

    thank you, sorry for my bad grammatical
    (4 votes)
    Default Khan Academy avatar avatar for user
  • starky sapling style avatar for user Domify
    Is British Columbia a primary or secondary succession
    (3 votes)
    Default Khan Academy avatar avatar for user
  • aqualine ultimate style avatar for user Animalia
    A good example of complete ecosystem recovery is the recovery of life around Mount St. Helens after it went KA-BOOM!
    (4 votes)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user mishiyasmin011
    Are Ecological succession and Evolution same terms?? If not! so,what are the difference b/w them??
    (3 votes)
    Default Khan Academy avatar avatar for user
    • blobby blue style avatar for user joshua
      Ecological Succession generally refers to the environment's, or the natural community's changes over time.
      For example, Volcano -> Island as mentioned in the video. The mix of species has changed, which is an ecological succession since initially there is no animal nor plants, but afterward there's animals etc.

      Evolution typically refers to the change of a species population's characteristic. This is basically the bird mentioned in the previous video "Environmental Change and Adaption".
      (4 votes)
  • blobby green style avatar for user 121098
    what is sucession?
    (3 votes)
    Default Khan Academy avatar avatar for user
    • starky sapling style avatar for user K.L.F
      Primary succession is when an ecosystem starts in a new place that previously had little to no life at all, and secondary succession is when an ecosystem is growing back from an ecological disturbance suck as a disaster
      (3 votes)
  • blobby green style avatar for user alexande.reid
    what is the general meaning of succession
    (3 votes)
    Default Khan Academy avatar avatar for user
    • duskpin tree style avatar for user offspringthe1st
      Succession in a nutshell is where organisms colonize a place that does not have any organisms currently. Primary succession is when this is happening for the first time in an ecosystem, and secondary succession is when this is happening after some kind of disaster and the organisms are taking back the ecosystem.
      (3 votes)

Video transcript

- [Voiceover] You look at a community that is in a given habitat, a natural question is to say, well, has that community always been that way? Has it always been there? Was there a time where maybe there was no life there? And the answer is, well, yes, the communities do change over time, and there is some initial period where there might not be any life in that habitat, and then life slowly colonizes it, and the makeup of that life will change over time, the makeup of that community. And this general idea is called ecological succession. Ecological succession. And folks will often talk about the different types of ecological succession, splitting it up into primary ecological succession, and so primary is when you start with no life, because you really have a new habitat, and then slowly life colonizes it. And the best example of that, or one of the best examples of that is when new land forms due to lava flows. There are pictures from Hawaii, where new land is forming as this lava hardens. And, at first, there is, when it's molten lava, there's no life there, then it hardens, and slowly, basic life, or life in general, will start to colonize that lava rock. And some of it you won't be able to see with your naked eye, it would be microbes, and some of it you could see, it could be simple ferns and plants like that, and these are often called the pioneer species. But what they often do is make that environment more suitable for other types of life. So they might slowly break down that rock. As they die, along with the broken down rock that also gets eroded from the water and the air and the rain, it starts to make soil and conditions more suitable for other types of species. And these pioneer species, they don't even have to just be plants and microbes. I was just reading an article about how in Hawaii, humans want to get that land because it's beachfront property. Or the beach might not have formally formed in the traditional sense, but you have ocean view property. So humans might be some of the first pioneer species who might wanna be out on that land. And that new land doesn't just form from lava flows. There are other examples of new habitats forming. So right here, we have pictures of a new habitat forming because of the retreat of glaciers. When the glaciers were covering up these rocks, you didn't have life on them. But as the glacier retreats right over here, you see things like these mosses and other types of pioneer species starting to colonize. And over time, they're going to make it more and more suitable for other types of species. So that's primary succession. Another situation is when you have secondary succession. And there's many different ways you could have secondary succession. One of the most cited examples is when you have some type of a disaster. And so this right over here, this is a picture of a fire, so here, we're talking 'bout secondary succession, where you had a community, but then you have a fire, and so that fire might wipe out a lot of the community. And then it creates space for other things to form. So after you have a fire, the forest might look something like this, and then, notice, you have species that start to colonize where a lot of other species might have died or died during the fire. And sometimes, after this disaster of some kind, you might get back to the same type of community that you had before the disaster, but sometimes, it could be a completely different one, that the communities don't come about in exactly the same way. So the general idea is communities change over time, we have ecological succession. There are times where there's no community, and then they come in, that's primary succession. And then, you have times where you have disasters of some kind that could change the environment in some ways, and it could change the makeup of that community. And things don't have to be as dramatic as new land formation because of lava or because of forest fires or even glaciers retreating. It could because of a disease, or it could just be because a new species gets introduced somehow that changes the makeup, changes the competition, the predatory, the various, the symbiotic dynamics within that community.