Do you know the boundaries of the planet we call “home”?

In the mid-2000s, Johan Rockström and a group of 28 internationally renowned scientists introduced the planetary boundary framework to identify the nine processes that regulate the Earth system’s stability and resilience and to quantify the ‘safe operating space’ where people and the ecosystems we’re part of can thrive.

The composition of terrestrial biomes is one of these systems, and forest biomes, in particular, have strong feedbacks that impact regional and global climate systems. But, through ‘land-system change’, humanity increasingly puts the vital ecosystem functions that forests provide at risk. What transgression means for the living biosphere and if and how we can return to a safe state is something we’ll explore in this post – the third in the series “Know your planetary boundaries”.

But before we go there, know there is much more to this topic; check out our previous posts for a short overview of all planetary boundaries, the previous ones on climate change and biosphere integrity, and more information on climate tipping points & feedback loops and the human climate niche.

A human-dominated planet

Humans are now the dominant force of change on the planet, and we are only starting to fully comprehend how significantly our activities impact the climate and ecosystems and what this means for current and future generations.

After centuries of conversion, fragmentation and degradation of natural ecosystems, the planet can no longer meet our high demands. We are now in a delicate situation where we need a strong and resilient biosphere to help us mitigate and adapt to the changing climate, but it’s weaker than ever.

Resilient ecosystems regulate the climate, nutrients, air, and freshwater quality and buffer against the impacts of natural disasters. But now that we have converted half of the Earth’s ice-free terrestrial land into agriculture, and with large swathes of “intact” land being naturally barren, there is actually not a lot of nature left to back us up.

The world has already lost 40% of its forest cover.

Forest biomes are home to more than 80% of all terrestrial species of animals, plants, and insects and play an essential role in global and regional climate regulation. By acting as carbon sinks and sources of water vapour, they cool and stabilise the world’s climate and provide us with fresh water. Yet, forest loss continues to grow, and today, the world has already lost 40% of its forest cover.

When it comes to conserving natural lands, we must retain 75% of forests globally to stay within planetary boundaries. With only 60% standing and much of the remaining forest cover being fragmented, degraded, or weakened, some forests have already started to turn into savannas or grasslands. On a biome level, the boundaries of seven out of eight major forest biomes have been crossed, with tropical forests in Asia and Africa showing the highest level of degradation.

The transition from forest to savanna or grassland is called a regime shift. Such a shift can occur when compounding human activities and climate change impacts push forests past a threshold, triggering amplifying feedbacks that result in rapid forest dieback. Several studies show that the Amazon rainforest is close to such a tipping point, and even subtle changes in structure, composition, and functioning could majorly affect the global carbon and water cycles.

The forest-rainfall and fire-vegetation feedbacks drive the savannisation of the Amazon Rainforest. Forest cover loss decreases evapotranspiration and moisture flow downwind. This lowers regional rainfall, leading to forest dieback and an open vegetation state. Without the cooling and moistening effects from closed canopies, the air dries out, grassy fuels grow, and fires spread easily. Once trees disappear, fires occur more often, preventing regrowth.

It’s time to act!

The scale of our negative impact on the world’s ecosystems is enormous. We can get back into the safe operating space for land-system change and, at the same time, mitigate climate change and halt rapid biodiversity loss if we halt all degrading activities, protect what we have and restore what is lost. It is time to act because our own survival depends on it.

Many countries have pledged to restore the land and halt deforestation by 2030, but they are not on track. Forests are slowly recovering in some areas, but cutting down one hectare of rich tropical rainforest elsewhere cannot be offset by reforesting or afforesting trees in a temperate climate at home.

Our global food system is the primary driver of the transgression of the forest boundaries. Studies suggest it’s possible to feed a growing population on less land, but that will require us to reduce food waste throughout the production and supply chain, allocate cropland to the most productive regions, control processes causing the loss of fertile land, and manage demand-side factors. Moving to a diet that excludes animal products has transformative potential, reducing food’s land use by 75%.

We could discuss much more, but this is all we could fit into a single Instagram carousel. Have you seen it already? Scroll through our slider below, and let us know what you think through one of our social channels – we like to hear from you!

Next up is the planetary boundary freshwater change.