Disturbance and movement

Tree falls can create gaps and disturbance in rain forests.

Written by Thary Gazi Goh
Photos by Thary Gazi Goh & Langur Project Penang

The natural world is chaotic. Accidental events can happen that can affect a whole ecosystem, for example a fire started by lightning or a disease that kills off a species. In the worst cases, random events can cause the collapse of entire ecosystems.

The effects of random events on ecosystems become stronger the smaller the area is. This means that small isolated forest patches will take more damage from accidents than larger areas. 

So why have our forests not been completely wiped out by random events? Two factors come into play: Movement between different ecosytems and heterogeneity. 

Movement of biodiversity between separate patches helps to recover damaged ecosystems. When all the vegetation was removed from Krakatoa after a massive volcanic eruption, the surrounding islands contributed to the recovery of the ecosystem there.

Natural rain forests are highly diverse.

Heterogeneity means more diversity of species. More heterogenous ecosystems are also more resilient. If a plant disease like fusarium wilt hits a monoculture banana plantation all the plants will be wiped out, if it hits a diverse rainforest there will be minimal damage.

This happens because there are more varied plants and they are far apart enough so disease doesn’t spread like a wildfire. In fact literal wildfires tend to spread less effectively in heterogenous forests because different plant species have different reactions to fire and some patches can act as natural fire breaks.

Canopy bridge stretches across roads with fast-moving cars
Malaysia’s first canopy bridge built by teams from Langur Project Penang and APE Malaysia

Photos credit to Langur Project Penang
Learn more on Malaysia’s road ecology and wildlife canopy bridge here

Canopy bridge provides a safer way for animals to cross a busy and dangerous road
Photos credit to Langur Project Penang

In terms of understanding how to apply this to our cities, it is really important to not just preserve forest patches, but to allow for some form of connection. This can be through bee lanes (margins planted with flowers to allow for pollinator movement), viaducts (tunnels that allow the movement of ground animals) or canopy bridges (rope bridges that allow movement of arboreal animals).

This is not just a matter of building structures, barriers can be removed through collective action like closing roads on certain days of the month or turning off non-essential lights during a migration or mating season.

In Kuala Lumpur most of our forest patches are abandoned rubber plantations, we can increase their resilience by planting a greater variety of tree species and slowly transitioning away from a monoculture plantation to diverse secondary forests.