What is the Forest Transition Curve?

Explore the relationship between trees, humans and ecosystem services over time

By The CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

The forest transition curve (2011-01-02) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

The Forest Transition Curve...

was created by FTA scientists to understand how human activities affect the landscape over time. It allows researchers to predict the effects (positive and negative) of economic development on tree-covered landscapes. 

Oil palm plantation (2017-01-20) by Nanang Sujana/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

As tree-cover decreases, so do ecosystem services

Complex land-use decisions that affect forests today will impact ecosystem services including carbon storage, soil improvement and water-cycle regulation for decades. Once lost, these benefits can return slowly with reforestation and agroforestry.  

There are six stages of the Forest Transition Curve:

Old-growth forest (2021-10-22) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

1. Old-growth forest

These landscapes, also known as 'primary forests,' are mostly untouched by humans. They offer the greatest ecosystem benefits on the forest transition curve and store vast carbon stocks. 

Gunung Halimun-Salak National Park (2013-01-30) by Mokhamad Edliadi/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

Mount Halimun Salak National Park

This 400 km2 conservation park in West Java province, Indonesia is a water catchment area, providing clean drinking water to the surrounding area. It also homes a wealth of biodiversity including species such as Javan leopards and silvery gibbons. 

Logged forests (2021-10-23) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

2. Logged Forests

This is where the degradation curve begins. Semi-logged forests are less biodiverse and offer fewer benefits compared to old-growth forests. The arrival of humans may also expose forests to greater risks and illegal logging in the future. 

Deforestation in Democratic Republic of the Congo (2018-06-16) by Axel Fassio/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

Deforestation in the Democratic Republic of the Congo (DRC)

These trees were cut down for timber near a project site for the FORETS initiative in Weko, Democratic Republic of the Congo (DRC). The striking difference between logged ground and old-growth in this picture illustrates how fast forest transitions can happen. 

Secondary and agroforest (2021-10-24) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

3. Secondary and agroforest

Secondary forests are those in the process of growing back after a period of deforestation. Agroforests occur where trees are intentionally planted on or near agricultural land so the crops can benefit from forest ecosystem services including soil improvement and shade. 

Farm workers (2018-03-07) by Marlon del Aguila Guerrero/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

Agroforestry in Peru

These farm workers are heading to their next job on an agroforestry farm in Loreto, Peru. Farming that incorporates trees is one way to preserve ecosystems while also improving livelihoods. The trees on agroforestry farms often produce valuable products to sell, for example.

Annual crops (2021-10-25) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

4. Annual crops

Agriculture is essential to feed earth’s expanding population. However, when too much land is converted from forests to monocrop farms, most of the ecosystem services of the original forest are lost. 

Durum wheat varieties (2015-11-28) by Unknown/Biodiversity Alliance & CIATThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

Durum wheat varieties in Ethiopia

In this example of annual crops, farmers in Ethiopia are growing and testing different wheat varieties, including durum, to see how adaptable they are in different climates. This is important because biodiverse crops are more resilient; if one variety dies, another may survive. 

Grasslands (2021-10-26) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

5. Grasslands

When farm-soil nutrients are depleted, the land must be left to either grow back with grasses and shrubs or enriched with large amounts of fertilizer, which pollutes the environment. If left to grow, grasses bring back some of the lost ecosystem benefits of the forests. 

Grasslands in DRC (2018-06-15) by Axel Fassio/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

A grassy rise near Yangambi

These grasslands near Yangambi, Democratic Republic of the Congo (DRC) maintain ground cover for the soil and offer food to migratory animals. 

DID YOU KNOW? Grasslands are important and valuable ecosystems where they occur naturally. For example, the Serengeti National Park in Tanzania is home to countless animals such as zebras, leopards and hippos. However, when grasslands replace forests, it means the natural ecosystem and its services have been degraded. This can have a negative impact on local biodiversity and contribute to climate change.

Mosaic landscape (2021-10-27) by FTAThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

6. Mosaic landscapes

When carefully managed, a mosaic of tree plantations, agroforests and wood farms – forests that are planted in order to harvest wood – can begin restoring some ecosystem benefits that were lost from old-growth forest.  

Tribudi Syukur village (2017-11-05) by Nanang Sujana/CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

Tribudi Syukur village, Indonesia

Mosaic landscapes like the one pictured have the potential to restore ecosystem services while also allowing societies to develop sustainably and produce the food they need. This landscape approach is key for humans to co-exist and thrive together with the natural world.

Learn more about how people in Halimun Salak National Park, Indonesia, have used a landscape approach to both conserve forest ecosystems and develop industries.

The landscape approach: what, where, how? (2017-08-17) by CIFORThe CGIAR Research Program on Forests, Trees and Agroforestry (FTA)

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