Bees · Death · Extinction · Flowers · Food Chain

Trophic Cascade

I didn’t even realise this thing had a name.

Trophic cascades occur when predators in a food chain alter the number of prey available. For example, if there are a surge in the number of fish in a lake, there would be fewer smaller fish as more would be eaten, or vice versa. This would also have effect on the plankton available as it is not being eaten so will therefore be higher in numbers, taking effect on their prey and so on.

It is an ecological concept that is important in understanding the knock-on effects of removing certain predators or prey, which is what is usually a consequence of human activity (over fishing/pollution/etc).

top-down cascade is a trophic cascade where the food chain is disrupted by the removal of a top predator or a third/fourth level consumer.

bottom-up cascade occurs when a primary producer or primary consumer is removed and there is a reduction of population size through the community.

The theory was first introduced by Aldo Leopold. He first described the mechanism of a trophic cascade based on his observations of overgrazing of mountain slopes by deer after the human extermination of wolves. Nelson Hairston, Frederik Smith and Lawrence Slobokin are credited with introducing this concept into scientific discourse. Green world hypothesis argues that predators reduce the abundance of herbivores, allowing plants to flourish. This brings attention to the role of top-down forces (predation) and indirect effects in shaping ecological communities.


  1. In North American lakes, piscivorous fish can dramatically reduce populations of zooplanktivorous fish, zooplanktivorous fish can dramatically alter freshwater zooplankton communities, and zooplankton grazing can in turn have large impacts on phytoplankton communities. Removal of piscivorous fish can change lake water from clear to green by allowing phytoplankton to flourish.
  2. In Pacific kelp forests, sea otters feed on sea urchins. In areas where sea otters have been hunted to extinction, sea urchins increase in abundance and kelp populations are reduced.
  3. A classic example of a terrestrial tropic cascade* is the reintroduction of gray wolves (Canis lupus) to Yellowstone National Park, which reduced the number, and changed the behavior, of elk (Cervus elaphus). This in turn released several plant species from grazing pressure and subsequently led to the transformation of riparian ecosystems.

*Terrestrial trophic cascades were restricted to communities with relatively low species diversity, in which a small number of species could have an overwhelming influence and the food chain could operate as a linear food chain


Bee Food Chain

The one main thing in this food chain is the BEE – without them, flowers would die, meaning plants would die, meaning several species would die.

Their extinction would have a catastrophic effect on the ecosystem globally.



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s