In his seminal piece — Collapse — Jared Diamond documented how a number of civilizations who failed to protect their forests ultimately also experienced severe systemic decline.

Forests provide innumerable ecosystem services. They filter the air and water, provide a habitat for helpful plants and animals, prevent erosion, sequester moisture that enables healthy rainfall patterns. To keep forests safe and to nourish them is to keep the land itself safe. To keep life safe. To, ultimately, keep human civilizations safe.

In other words, a city or nation cannot healthily exist without healthy forests to support it.

Mistreated Tropical Forests become Carbon Source

From the point of view of confronting climate change, maintaining healthy forests is also essential. Healthy forests sequester more carbon — keeping that carbon locked in plants and soils. Unhealthy forests do the opposite — they release carbon stored over years and decades.

Since time immemorial, short-sighted forms of human civilization have harmed forests by cutting down too many trees, by killing off the creatures that support healthy forests, or worse, by burning the forests down. Ultimately, most of those civilizations also cut their own life-spans short. In the present day, we see this kind of harmful activity throughout the tropics. And, as a result, the tropical forests which have done us such an amazing service by drawing down a substantial portion of the fossil-fuel based carbon emission are ailing.

(In this image from Earth Nullschool, we can see high present carbon dioxide concentrations at the Earth’s surface. High CO2 concentrations show up in light colors. Low CO2 concentrations show up in dark colors. As you can see in the above image, the rainforest regions of the Amazon and Equatorial Africa are presently drawing down a considerable amount of atmospheric CO2 — which is generating a lower local concentration. That said, these forests do not draw down as much carbon as they used to. They have been disrupted by harmful human activity such as clear cutting and hunting of key species. As a result, through decay, fire, and drought, these forests are now emitting more carbon than they take in on net.)

According to a recent report out of the journal Science, about 425 million tons of carbon are being released, on net, from tropical forests around the world each year. This is equivalent to about 4 percent of global human emissions (primarily from fossil fuel burning) of around 11 billion tons of carbon each year. In other words, poor forest management is already amplifying the impact of fossil fuel based climate change.

The tropical forest carbon release occurred between 2003 and 2014. Study authors noted in The Guardian:

“This shows that we can’t just sit back. The forest is not doing what we thought it was doing. As always, trees are removing carbon from the atmosphere, but the volume of the forest is no longer enough to compensate for the losses. The region is not a sink any more.”

These same authors attributed this turning of a net carbon sink into a net carbon source primarily to poor land management practices. Primary sources of harm and loss involved the “thinning of tree density and the culling of biodiversity below an apparently protected canopy – usually as a result of selective logging, fire, drought and hunting.” More of the forested land has been turned over to developers and hunters when the land should have been set aside for protected parks and for the use of indigenous peoples whose ways of living help to support forest ecosystems.

An Urgent Need to Rapidly Cut Carbon Emissions While Restoring Healthy Forests

While human-caused climate change is now adding pressure to tropical forests, poor land management is presently a greater source of harm. In the past, sustainability-minded scientists had assumed that tropical forests would remain mostly functional as a carbon sink until warming approached 3-4 C above late 19th Century averages. At that point, heat alone will be enough to wring carbon out of these forests on net. But harmful human activity has pushed that time forward to the first decade of the 2000s.

Ultimately, the early failure of forests as a tropical carbon sink means that there’s less of a so-called carbon budget available. At this blog, we have long asserted that the effective carbon budget for a safe Earth at this time is basically zero. What this means is that some bad climate outcomes such as worsening weather, reduction of habitability in the Equatorial and near-Equatorial region, possible disruptions to growing seasons, declining ocean health for at least the next century, and sea level rise forcing mass abandonment of coastal settlements are already possible, likely, or happening now. Any addition of carbon thus makes an already troubling situation worse. That said, rapid cuts to fossil fuel emissions can still prevent worse outcomes such as more rapid sea level rise, much worse weather, very extreme heat rendering large regions practically uninhabitable for present societies, and a potentially worst-in-class global mass extinction associated with a hothouse ocean anoxic event.

(How removal of large animals through hunting and poaching can harm a forest’s ability to sequester carbon. Image source: Carbon Brief.)

Present science pointing toward loss of Tropical forests as a carbon sink means that our window is, again, rather smaller than past scientific oracles previously identified. The urgency for rapid carbon emissions cuts, therefore, could not be greater. But we also need to protect and restore forest vitality — which will be necessary to help the natural world bounce back from the insult we’ve already produced.

From study author Wayne Walker:

“We need to be positive. Let’s turn tropical forests back into a sink. We need to restore degraded areas. As far as technology for reducing carbon is concerned, this is low-hanging fruit. We know how to protect and sustain forests. It’s relatively cost effective.”

To be very clear, without emissions cuts to zero and subsequent atmospheric carbon drawdown substantial enough to prevent 3-4 C warming, these forests will eventually be in trouble due to the very harmful impacts of rising heat alone. So we need to do both. And we need to do it now.

Links:

Tropical Forests are Now a Net Carbon Source

Alarm as Study Reveals Tropical Forests are a Huge Carbon Source

Earth Nullschool

Carbon Brief

Collapse

Hat tip to Umbrios