• The Listener
  • North & South
  • Noted
  • RNZ
Lord of the forest: Tāne Mahuta is more than 50m tall. Photo/Shutterstock

The value of forests: How trees reduce anxiety, boost brain function and help power the planet

Trees are not only life-supporting but also vital to our emotional wellbeing, reducing stress and boosting brain function. Yet they are under siege.

It is an enchanted elven forest, says Australian bush expert Mark Graham, largely unchanged over tens of millions of years. “So, we are back to the dawn of the evolution of flowering plants and songbirds, back to the time of the dinosaurs.”

An ecologist with the Nature Conservation Council of New South Wales, Graham owns a private conservation reserve on the Dorrigo Plateau, part of the Gondwana Rainforests of Australia, a Unesco World Heritage Site.  These rainforests covering 3665 sq km of NSW and Queensland are some of the oldest on the planet, one of the few remnants of the supercontinent of Gondwana that broke up about 180 million years ago.

“The songbirds in this part of the world are some of our most ancient,” Graham says. “Listening to the dawn chorus in this forest is like having a window back in time.”

Now, instead of songbirds, he hears the roar of fire just 500m from his home. “I have never heard anything like it. It is like Mother Nature is so angry she is growling with the deepest, most guttural tones.”

Tāne Mahuta. Photo/Supplied

These rainforests are not meant to burn; they have been wet for tens of millions of years. But burning they are. More than a quarter of a million hectares have been scorched by flames and Graham expects thousands more hectares to burn as Australia experiences record-breaking temperatures.

The damage is a global tragedy. Although birds can fly elsewhere, there are few refuges for the ancient fauna species that live deep in wet leaf litter. “Frogs, ancient lizards and snakes have no capacity to survive fire, they just get cooked. Some plant species have the capacity to regrow, but some of the really delicate species that require permanent moisture, such as the ferns, will probably die out.”

This is not part of an age-old cyclic pattern of wildfires. This is drought, wind, high temperatures. Climate change?

“Absolutely. These fires are off the charts, there is no historical reference point, we are in uncharted territory in terms of the extent of country that has burnt, the severity of the fire, the range of ecosystems affected, the altitudinal range of the fire, the number of houses lost.”

Across New South Wales, out of a total of 1.9 million ha of national park land, more than three million hectares have succumbed to fire since July, including 20% of the Blue Mountains. Eight people have been killed.As early as November, smoke from bushfires clogged the air over Sydney, setting off smoke alarms, cancelling sports events, delaying ferry services and flights in and out of the city and triggering health warnings.

Read more: Prominent Kiwis share stories about the trees they love | The most incredible trees from around the world

Top-selling artist Tim Wilson’s Haast, one of many images of trees in pristine New Zealand landscapes that have gained him international recognition. Wilson believes people respond to the “emotional impact” of light filtered through trees. Photo/Supplied
Australia is just one of a rash of red spots on the Global Forest Watch fires map. From Lebanon to California, from France to Siberia – one of the coldest places on Earth – fires have been destroying forests. Data from the satellite-driven Sentinel-3 World Fire Atlas recorded 79,000 fires in August 2019, compared with just over 16,000 fires during the same period last year. Of these, almost half were in Asia, about 28% in South America, 16% in Africa, and the rest in North America, Europe and Oceania.

Eight hundred football fields of forest are lost every hour, and devastating fires are raging around the world, says former EU environment commissioner Karmenu Vella. He says forests are our life-support system, hosting 80% of the Earth’s biodiversity and standing at the frontline in reducing climate change. “But today, as never before, they are under severe threat. ”

Although most wildfires are caused inadvertently, deforestation for agriculture in countries such as Brazil and Indonesia is contributing to soaring greenhouse gas emissions.

And although planting trees is hailed as a counter to global warming, researchers say rising carbon dioxide will promote faster tree growth – which may mean a shorter tree life, reducing the amount of time carbon is locked away. The longest-lived trees are those with the slowest growth rates.

Let the sunshine in: studies show time in forests combats depression and lowers blood pressure. Photo/Getty Images
Slow-growing kauri belongs to one of the oldest living conifer families, Araucariaceae, which has a fossil record stretching back to the dinosaurs. Kauri ancestors seem to have evolved in the Australia-New Zealand region about 135 million years ago, when the two countries were still close together as part of Gondwana. Although most of New Zealand’s land mass was under water during the Oligocene period, about 23 million years ago, kauri provides the greatest evidence for at least an archipelago of islands remaining. Molecular gene sequencing shows that kauri became genetically distinct from its closest Australian relatives well before the Oligocene drowning. It is a living link with New Zealand’s most distant past.

When humans first arrived in New Zealand, forests covered about 80% of the country. By the end of the past century, this had been whittled down to just over a quarter, concentrated in mountainous and hilly areas on the conservation estate or in remnant patches held on public reserves or covenanted on private land. Even within these remaining areas, pests – stoats, rats, feral goats, deer and possums – and diseases such as kauri dieback and myrtle rust are all taking their toll. Wilding pines are changing our landscapes and out-competing native forests.

As the pressure on the world’s forests mounts up so, too, do arguments for their survival. Forests play a critical role in mitigating climate change. They purify the water and air, absorb carbon and cool the environment through a process of water evaporation (or evapotranspiration). They provide jobs and food and are habitat for 80% of the world’s land-based species, including African forest elephants and rhinos.
Flowering pōhutukawa symbolise the New Zealand summer. Photo/Getty Images

They also calm our shattered nerves. The ancient Japanese practice of shinrin-yoku or “forest bathing” is recommended in self-help manuals and science journals as new research suggests spending time in forests reduces stress and boosts mood, creativity, mental health, immune and cognitive function. Time in forests reduces depression and anxiety and improves physical wellbeing – the Royal Botanic Gardens in Melbourne now offers forest therapy for $36 a pop.

In Washington DC, journalist Florence Williams, a fellow at the Center for Humans and Nature and author of The Nature Fix, has been promoting the importance of time spent in wild places, even the local city park.

“Humans have an innate association with these landscapes,” she says from her home close to one of DC’s many city parks. “Even subconsciously, our brains and perceptual systems understand landscapes and feel comfortable in them. City planners need to recognise this as a priority for the health of our communities and our people. We know [anxiety and other mental health problems] are worse in cities and we know access to nature can calm our nervous systems and those parts of the brain that get overactive in the city.”

For her book, she travelled to South Korea, Japan, Scotland and Finland, looking at the range of programmes, new and old, aimed at meeting our apparently deep-seated need for a dose of intense nature. Most of them take little effort. You walk into the forest – no cell phone, no playlist, no traffic. You listen to the birds, watch the movement of light on the leaves, feel the coolness of the air, pause and breathe – deeply.

Te Waha O Rerekohu, left, at Te Araroa, is thought to be the oldest living pōhutukawa, at about 600 years old. Photo/Alamy

Back at home, Williams trawled through a wealth of medical data. Increasingly, she says, scientists are quantifying nature’s effects not only on mood and well-being, “but also on our ability to think, to remember things, to plan, create, daydream and focus”.

Studies show time spent in forests reduces concentrations of the stress hormone cortisol, lowers the pulse rate and blood pressure, lessens levels of hostility and depression and, for children in particular, improves fitness and self-confidence. It does this on a number of sensory levels, says Williams. Aerosols in evergreen forests have been found to act as mild sedatives and stimulate respiration, the sounds of water and birdsong improve mood and alertness, and the colours and patterns of natural treed landscapes – as any Romantic poet would attest – are calming to the eye. Even videos of nature have been found to relieve stress and mental health and behavioural issues in prison inmates.

There were times when she was sceptical, says Williams, so it was a revelation “to realise how our surroundings can help prevent physical and mental problems”. She recommends a goal of five hours a month in nature (about two 30-40 minute periods a week) to counteract what she describes as an “epidemic” of dislocation from the outdoors – an epidemic that is damaging to our health and to that of the environment.

“If we recognise we need these ecosystems for our own health, it is yet another argument in support of conservation, because we are more inclined to protect something if we see more value in it. It is after we establish a true bond with these places and an understanding of how connected we are that we can really start to care about them.”

Rata trees in flower near Fox Glacier. Photo/Andris Apse
Over the past decade a rash of new books has been hammering home the importance of trees. In The Man Who Planted Trees, journalist Jim Robbins, of the New York Times, tells the true story of a man on a mission to reforest the world by cloning the oldest, largest and most resilient trees. US scientist Daniel Chamovitz demonstrates how plants respond to touch, sound, smell, sight and even memory in What A Plant Knows. Richard Powers’ mythic The Overstory, winner of the 2019 Pulitzer Prize for fiction, has trees as revered ancestors – slow, interconnected, resourceful.

In 2016, German forester Peter Wohlleben put scientists into a spin with his hugely popular The Hidden Life of Trees, in which he argues that, to better protect our forests, we need to acknowledge that trees have vibrant inner lives not so different from our own. They thrive in families, he says. They form social networks, care for each other and send out signals about drought, disease or encroaching herbivores. Such comments are supported by recent research into the way trees communicate with each other, above and below ground. Scientists have found trees do “share” water and nutrients through microscopic networks of fungal filaments (Wohlleben calls it the “wood-wide web”). It is a symbiotic relationship. The fungi feed on the sugar that trees photosynthesise from sunlight; the trees absorb the nitrogen, phosphorus and other mineral nutrients taken up from the soil by fungi. Research at the University of Lausanne, Switzerland, into the chemical, hormonal and slow-pulsing electrical signals emitted by trees, reported in the Smithsonian last year, has identified a voltage-based signalling system “that appears strikingly similar to animal nervous systems”.

The Hidden Life of Trees sold more than 800,000 copies in Germany and topped bestseller lists in 11 other countries. But Wohlleben’s anthropomorphic language infuriated others. He talks of “mother trees” feeding their saplings with liquid sugar, of trees forming “friendships” and nourishing sick individuals. Much like a herd of elephants, he writes, trees “look after their own, and they help their sick and weak back up onto their feet”.

Dense bush flanks the Waimakariri Gorge. Photo/Getty Images

In 2017, two German scientists launched an online petition to challenge these claims. The petition, titled in English “Even in the forest, we want facts instead of fairy tales”, said the book promotes “a very unrealistic understanding of forest ecology”. In the long term, they said, “the environment in general and forests in particular will not be helped by the sort of unenlightened thinking promoted by the hidden reality of this book.”

But if the semantics are questionable, Wohlleben’s motivation is not. If we recognise trees’ “emotional lives and needs”, he writes, “we will stop seeing forests as timber factories, and understand how forests can serve as oases of respite and recovery.”

The current “anthropogenic ecological crisis” also lies behind Plants as Persons, by botanist Matthew Hall, now associate director of research services at Victoria University of Wellington. In the book, he calls for a more harmonious relationship between humans and nature to avoid the “banal, unthinking scorched-earth policy” that we have inflicted on our plants and our planet.

Acknowledging plants as sentient beings, he argues, is a start. “Of course, we still have to use plants for food, shelter, medicine and clothing, but our first step is to recognise that we are taking a life. A key feature of many indigenous cultures is that the harm done to individual plants is not ignored or backgrounded.”

A road carved through the forest. Photo/Getty Images

In his new book, The Imagination of Plants, he plumbs the world’s religions and mythic traditions to expose the many examples of a deep-seated respect for, and kinship with, plants. It includes stories of gods creating plants and humans (Māori trace their whakapapa back to Ranginui and Papatūānuku, from whom the forests then humans were created); of first humans fashioned from wood (elm in Nordic countries, broom in Wales, ash in early Greece); of tree worship (including the many trees associated with Buddha); of metamorphosis from plant into human form; of trees that speak or weep. A new wave of contemporary tree-loving paganism – Hall applauds Prince Charles’ habit of wishing every tree he plants the very best – suggests a reawakening “of some kind of existential need to reconnect with these habitats that we are losing”.

As with Wohlleben’s loving, nurturing, grieving trees, calls to recognise plant sentience and reconsider the “moral standing” of plants are an easy target for derision. But as fires continue to burn and trees continue to be felled, a growing recognition of our reliance on forests, and the cultural traditions that encourage protection of forests, are already prompting a wave of tree-planting and forest-restoration activities. Even the recognition of the forested land of Te Urewera as holding the same “rights, powers, duties, and liabilities of a legal person” under the Te Urewera Act of 2014 – can be seen as a change in the value we place on our forests.

Williams is not so sure: “I don’t think you need that spiritual connection to appreciate and value landscapes and feel comfortable in them. I don’t want nature to seem precious and inaccessible. It can be the shrub in the backyard, it can be the sunset. But it is also about attentiveness. I try to encourage some practical ideas for how to open your senses and be present and mindful in the outdoors.” That is where research shows you get the benefits, by paying attention – and seeing the wood for the trees.

This article was first published in the January 11, 2020 issue of the New Zealand Listener.