Mangroves are many species of tree adapted to living in salty water along coastlines and tidal rivers not far from the equator. They are remarkable in many ways and confer a host of benefits to their habitats. Here are some significant ones.

Mangroves and mangrove habitats play a major role in protecting coastal settlements from storm surges and waves. Mangroves significantly reduce the energy of waves, lowering wave height inland, including from tsunamis, and reduce surges from tropical storms. We took a boat through the mangroves in Southern Vietnam once, and it was an eye-opening maze of channels and islands. I could see how they act like a natural breakwater.

Mangroves help stabilise land from erosion. This helps plants and fauna inland make their homes. Mangrove root systems also trap sediment brought downriver or from the sea, building their environment and creating peaty soil when they decay.

Their incredible prop root network creates a wonderful sheltered space for marine wildlife to grow and develop. The nooks and crannies help protect young from predators until they are older and can better fend for themselves. This protective environment increases populations and helps local fishers and communities. The calm and sheltered waters inside mangrove habitats also provide sanctuary for birds and a host of other non-marine wildlife.

Mangroves are an excellent carbon sink. They capture carbon as they grow, and the low-oxygen sediments deposited beneath them help lock carbon away.

I've contributed to plant trees through Eden Projects with a portion of any monthly or one-off support I receive. I wanted to explain Mangroves partly because, as of July 2023, together, we've passed 26,000 trees planted, most in mangrove restoration projects in Madagascar, and provided over 350 work days for locals.

"Madagascar is one of the world's top biodiversity conservation priorities because of its endemic species and severe habitat loss rates. Restoration in Madagascar is important because the destruction of the mangrove estuaries along the coastline has caused mudflats to wash into the ocean, destroying once-productive fisheries and increasing the vulnerability of coastal communities to hurricanes, tsunamis, and floods. In the dry deciduous forests, deforestation threatens one of the world's rarest and most diverse forest systems."

Mangroves make a real difference. To everyone who's helped make this happen, thank you!

Mangroves

Many trees and forests were built to live with fire and in many cases, fire is essential for a healthy ecosystem. Giant sequoias, for example, have cones that dry out during surface fires releasing their seeds so they can germinate at the ideal time to grow with less competition.

Ponderosa pines have a number of ways they have evolved to live with fire.

They have bark that when heated can split off from the tree protecting the trunk and reducing the spread of fire. 

They often lose lower branches, sometimes from smaller fires, reducing the likelihood of ladder fires that climb towards the crown.

The shade they cast and the acidic soil they favour helps reduce understory plants that could catch fire beneath the tree and help a fire to latch onto the main trunk.

They have deep roots that can remain intact after a fire allowing the tree to still gather water and nutrients even when surface roots are damaged.

Some policies of suppressing natural fires have changed the balance of many forest systems and helped promote some of the recent mega-fires.

More about the Fire ecology of ponderosa pines (pdf).

Also see: identify a douglas fir, time hierarchy

Ponderosa pine fire protections

A time hierarchy example is how durable dynamic systems have elements, or layers, that change at different rates.

Just like for pace layers, the fast layers that change quickly provide innovation, while the slower layers stabilise and remember.

In his short article Pace Layering: How Complex Systems Learn and Keep Learning, Stewart Brand gives this evocative example of the time hierarchy of a coniferous forest:

"Take a coniferous forest.  The hierarchy in scale of pine needle, tree crown, patch, stand, whole forest, and biome is also a time hierarchy.  The needle changes within a year, the crown over several years, the patch over many decades, the stand over a couple of centuries, the forest over a thousand years, and the biome over ten thousand years.  The range of what the needle may do is constrained by the crown, which is constrained by the patch and stand, which are controlled by the forest, which is controlled by the biome.  Nevertheless, innovation percolates throughout the system via evolutionary competition among lineages of individual trees dealing with the stresses of crowding, parasites, predation, and weather.  Occasionally, large shocks such as fire or disease or human predation can suddenly upset the whole system, sometimes all the way down to the biome level."

It's an example of his wonderful framework of pace layers, which he applies to the working structure of a robust and adaptable civilisation.

Time hierarchy

In some forests where the trees grow tall and straight, like those in the US Pacific Northwest, when a giant tree falls, it creates an opening in the forest canopy that lets in light for new growth to take foot. The mighty fallen tree trunks themselves provide a new surface for seedlings to take root, away from the competition of the forest floor. When this happens, the fallen tree becomes an integral part of a new ecosystem.

Such fallen trees are known as nurse logs. Sometimes, a nurse log is so successful as a nursery for the young trees that they will grow along the full length of the fallen trunk. When the original trunk finally decays, it leaves behind it a remarkable, straight line of trees.

Nurse log

What a lovely time of year—when the leaves of deciduous trees in many forests change from the deep greens of summer to the yellows, oranges and reds of autumn. But what makes the leaves change colour, and what compounds are responsible for nature's spectacular display?

Many of us will know the green of chlorophyll, but leaves also contain carotenoids. As the chlorophyll fades, the golden oranges of these carotenoids start to shine through. You may recognize one carotenoid, beta-carotene, from carrots.

Another carotenoid, xanthophyll, is responsible for the beautiful bright yellows.

The leaves of some trees also produce anthocyanin as autumn begins, which produces those beautiful deep reds.

This sketch features in my book Big Ideas Little Pictures

Autumn leaves and the compounds that cause their colours

If you lived on Easter Island, would you really cut down the last mighty tree knowing that would be it? It seems either foolhardy or desperate to knowingly cut down the last of a kind and your last source of timber. So how could it happen?

Jared Diamond, in his book Collapse and article Easter’s End, explains how this situation could happen through a gradual, hardly noticeable decline over many years. Those who remembered the great trees that they used to make rafts, canoes, and ships were old or had long since died. Today's trees may be nothing like the forests and towering trunks of tens or hundreds of years ago.

"Gradually trees became fewer, smaller, and less important. By the time the last fruit-bearing adult palm tree was cut, palms had long since ceased to be of economic significance. That left only smaller and smaller palm saplings to clear each year, along with other bushes and treelets. No one would have noticed the felling of the last small palm."

More recently, I read Rutger Bregman's story of Easter Island in his book Human Kind: A Hopeful History. In the chapter "The Mystery of Easter Island," he digs into the reconstruction provided by Diamond and others and questions whether the Easter Islanders really were reduced, after losing their trees, to infighting and destitution.

Bregman found evidence to suggest that rather than driving themselves to the brink of extinction, the Easter Islanders were likely still thriving when Peruvian slave traders arrived in 1862, and sixteen slave ships carried off a third of the island's population, 1,407 people.

Yet the worst for them was still to come a year later when the government was pressured to return the islanders home. A smallpox outbreak carried by the returning islanders wreaked devastation during the voyage, with hundreds dying at sea. The 15 islanders who made it home carried the virus with them, and it spread to the inhabitants who remained. He cites that the population was reduced to just 110 inhabitants in 1877 when the epidemic finally subsided.

Until the arrival of the slave ships, the population, despite their trials, was still thriving. Bregman suggests that it was, in fact, contact with the rest of the world that destroyed Easter Island.

For another thought-provoking perspective, Seth Godin asks who cut down the second-to-last-tree?

Who cut down the last tree?

I love this term. From the Japanese shinrin-yoku, it means to soak in the atmosphere of a forest. And I think it’s not too far of an overstatement to say that a walk in Nature is about the closest to a miracle cure we have. There appear to be myriad benefits from simply spending time in Nature. As my sister put it, if it was a drug we’d be prescribing it.

Though we didn’t call it forest bathing at the time it’s definitely some of my happiest memories, like here, here, here, here, and here.

Forest sketches