What if none of us but trees were left in this world?

Cooler cities

Across 293 European cities, ground under trees was 8–12 °C cooler than built-up areas in Central European summers, and trees cooled 2–4 times more than treeless green space.

The paper

Schwaab, J. et al. (2021). The role of urban trees in reducing land surface temperatures in European cities. Nature Communications 12. (opens in a new tab)

Wellbeing

In a survey of nearly 20,000 people in England, those who spent at least two hours a week in nature were more likely to report good health and high wellbeing.

The paper

White, M. P. et al. (2019). Spending at least 120 minutes a week in nature is associated with good health and wellbeing. Scientific Reports 9. (opens in a new tab)

Healing views

Hospital patients whose window looked out on a natural scene left hospital sooner after surgery and needed fewer strong painkillers than those facing a brick wall.

The paper

Ulrich, R. S. (1984). View through a window may influence recovery from surgery. Science 224, 420–421. (opens in a new tab)

Carbon uptake

The world’s forests took up about 2.4 billion tonnes of carbon a year between 1990 and 2007.

The paper

Pan, Y. et al. (2011). A large and persistent carbon sink in the world’s forests. Science 333, 988–993. (opens in a new tab)

Air filtering

In 2010, trees in the contiguous United States removed an estimated 17.4 million tonnes of air pollution, avoiding more than 850 deaths.

The paper

Nowak, D. J. et al. (2014). Tree and forest effects on air quality and human health in the United States. Environmental Pollution 193, 119–129. (opens in a new tab)

Pollinators

About 87.5% of flowering plant species, some 308,000 of them, are pollinated by animals.

The paper

Ollerton, J., Winfree, R. & Tarrant, S. (2011). How many flowering plants are pollinated by animals? Oikos 120, 321–326. (opens in a new tab)

Seed-caching birds

Jays plant oaks by burying acorns and forgetting some. Island scrub jays carried acorns up to 40% further in years with big acorn crops.

The paper

Pesendorfer, M. B. et al. (2016). Context-dependent seed dispersal by a scatter-hoarding corvid. Journal of Animal Ecology 85, 798–805. (opens in a new tab)

Caterpillars

Great tits time their chicks to the spring peak of caterpillars. In a Dutch population, springs warmed over 23 years but laying dates did not move, so chicks risked missing the feast.

The paper

Visser, M. E. et al. (1998). Warmer springs lead to mistimed reproduction in great tits (Parus major). Proceedings of the Royal Society B 265, 1867–1870. (opens in a new tab)

Aphids

Sugary honeydew from aphids changes the rain dripping through a spruce: under infested trees it carried more dissolved carbon and up to 46% less ammonium.

The paper

Stadler, B. & Michalzik, B. (1998). Linking aphid honeydew, throughfall, and forest floor solution chemistry of Norway spruce. Ecology Letters 1, 13–16. (opens in a new tab)

Great tits

A 47-year study of great tits in the UK found the population kept pace with fast-warming springs because each bird adjusted its behaviour to the conditions.

The paper

Charmantier, A. et al. (2008). Adaptive phenotypic plasticity in response to climate change in a wild bird population. Science 320, 800–803. (opens in a new tab)

Bats

By eating insect pests, bats may be worth billions of dollars to farming in North America.

The paper

Boyles, J. G. et al. (2011). Economic importance of bats in agriculture. Science 332, 41–42. (opens in a new tab)

Dormice

Hazel dormice fattening up for hibernation prefer hazelnuts to acorns, even though nuts take longer to open. Tannin-rich acorns made them lose weight.

The paper

Ancillotto, L. et al. (2015). Acorns were good until tannins were found: factors affecting seed-selection in the hazel dormouse (Muscardinus avellanarius). Mammalian Biology 80, 135–140. (opens in a new tab)

Lichens

Lichens are classic signs of clean air, but they come back slowly. After 20 years of falling pollution in Sweden, sensitive species had only partly returned, held back by poor dispersal.

The paper

Weldon, J. & Grandin, U. (2021). Weak recovery of epiphytic lichen communities in Sweden over 20 years of rapid air pollution decline. The Lichenologist 53, 203–213. (opens in a new tab)

Bark beetles

Warmer summers let spruce bark beetles fit in a second generation a year. By 2100 this could happen in southern Sweden in 63–81% of years.

The paper

Jönsson, A. M. et al. (2009). Spatio-temporal impact of climate change on the activity and voltinism of the spruce bark beetle, Ips typographus. Global Change Biology 15, 486–499. (opens in a new tab)

Spiders

The world’s spiders eat an estimated 400–800 million tonnes of prey a year, and those in forests and grasslands account for over 95% of it.

The paper

Nyffeler, M. & Birkhofer, K. (2017). An estimated 400–800 million tons of prey are annually killed by the global spider community. The Science of Nature 104. (opens in a new tab)

Wood-rotting fungi

Among wood-rotting fungi, the fastest growers are the fastest decomposers: how quickly a fungus spreads is the best single predictor of how quickly it breaks down wood.

The paper

Lustenhouwer, N. et al. (2020). A trait-based understanding of wood decomposition by fungi. PNAS 117, 11551–11558. (opens in a new tab)

Deadwood insects

Insects are behind about 29% of the carbon released from dead wood worldwide, around 3.2 billion tonnes a year.

The paper

Seibold, S. et al. (2021). The contribution of insects to global forest deadwood decomposition. Nature 597, 77–81. (opens in a new tab)

Mycorrhizal fungi

Trees that team up with ectomycorrhizal fungi are only about 2% of plant species, yet they make up roughly 60% of all tree stems on Earth.

The paper

Steidinger, B. S. et al. (2019). Climatic controls of decomposition drive the global biogeography of forest-tree symbioses. Nature 569, 404–408. (opens in a new tab)

Springtails

Springtails can reach 2 million per square metre in the tundra. Together they outweigh all wild land vertebrates about three to one.

The paper

Potapov, A. et al. (2023). Globally invariant metabolism but density-diversity mismatch in springtails. Nature Communications 14. (opens in a new tab)

Earthworms

Unlike most life above ground, earthworms are locally most diverse and abundant at higher latitudes, not in the tropics.

The paper

Phillips, H. R. P. et al. (2019). Global distribution of earthworm diversity. Science 366, 480–485. (opens in a new tab)