Grzegorz Lesniewski / Wintery dusk light over Mount Rozsypaniec. Bieszczady National Park, the Carpathians, Poland, January.

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Anup Shah / Sumatran orangutan (Pongo abelii) mature male 'Halik' aged 26 years sitting in a forest clearing watched from a tree by female 'Juni' aged 12 years. Gunung Leuser National Park, Sumatra, Indonesia. Re...

Laurie Campbell / Scots pine (Pinus sylvestris) mature tree in evening light, Abernethy Forest RSPB Reserve, Cairngorms National Park, August

Fiona Rogers / Proboscis Monkey (Nasalis larvatus) sub-mature male sitting in a tree. Bako National Park, Sarawak, Borneo, Malaysia, March.

Fiona Rogers / Proboscis Monkey (Nasalis larvatus) sub-mature male sitting in a tree. Bako National Park, Sarawak, Borneo, Malaysia, March.

Anup Shah / Proboscis monkey (Nasalia larvatus) mature male sitting in a tree, Bako National Park, Sarawak, Borneo, Malaysia, April

Anup Shah / Bornean Orangutan (Pongo pygmaeus wurmbii) mature male 'Nanang' suspended between a tree and a liana - wide angle perspective. Pondok Tanggui, Tanjung Puting National Park, Central Kalimantan, Borneo,...

Anup Shah / Bornean Orangutan (Pongo pygmaeus wurmbii) mature male 'Doyok' standing supported by a tree - wide angle perspective. Pondok Tanggui, Tanjung Puting National Park, Central Kalimantan, Borneo, Indonesi...

Andrew Parkinson / Scots pine (Pinus sylvestris) view from below of a mature tree covered in snow. Cairngorms National Park, Scotland, UK. February (non-ex)

Colin Varndell / Mature Beech tree (Fagus sylvatica) with leaves in autumn colours, Mark Ash Wood, New Forest, England, UK, October

Colin Varndell / Mature Beech trees (Fagus sylvatica) in spring, on beech avenue near Badbury Rings, Dorset, UK. May 2008

John Cancalosi / Winter scene with mature tree branches covered in snow, Herefordshire, England, UK, December 2010

John Cancalosi / Hoar frost covering ploughed field, with mature Oak tree (Quercus) and woodlands, Warwickshire, England, UK, December 2010

John Cancalosi / Hoar frost covering ploughed field, with mature Oak tree (Quercus) Warwickshire, England, UK, December 2010

Chris O'Reilly / Honey fungus (Armillaria mellea) mature, fruiting bodies on a fallen tree with person walking, Mixed woodland, Autumn, Derbyshire, UK, October

Aflo / N-5703 900-year-old European beech tree in field {Fagus sylvaticus} Bavaria, Germany.

George Sanker / Young Black bear (Ursus americanus) cub climbing mature fir tree, Yellowstone National Park, Wyoming, USA, May

Andrew Parkinson / Scots pine (Pinus sylvestris) a mature tree covered in snow, Cairngorms National Park, Scotland, UK, February

Jim Brandenburg / Giant Sequoia (Sequoiadendron giganteum), General Sherman tree in Sequoia National Park, California

Nigel Cattlin / Goat willow (Salix caprea) male catkins. Kennett and Avon Canal, Berkshire, England, UK. April.

Colin Varndell / Giant polypore fungus (Meripilus giganteus) fruiting at base of mature Beech (Fagus sylvatica) tree. Dorset, England, UK. October.

Sven Zacek / Oak (Quercus sp), mature tree covered with fresh snowfall, in evening light. Near Halliste River, Soomaa National Park, Viljandimaa County, Estonia. February.

Jack Dykinga / Arizona ash trees (Fraxinus velutina) along Romero Creek with a background of mature Saguaro cacti (Carnegiea gigantea) on the background ridges. Catalina State Park, Arizona, USA, December.

SCOTLAND: The Big Picture / Scots pine (Pinus sylvestris) saplings naturally regenerated from mature pines on moorland, Cairngorms National Park, Scotland, UK. August.

SCOTLAND: The Big Picture / Scots pine (Pinus sylvestris) saplings naturally regenerated from mature pines on moorland, Cairngorms National Park, Scotland, UK. August.

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) tree trunk, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) trees, Great Basin National Park, Nevada

Jeff Foott / Great Basin Bristlecone Pine (Pinus longaeva) tree, Great Basin National Park, Nevada

Nick Upton / Researcher using laptop to check trailcam footage of Siberian flying squirrel (Pteromys volans) nest box in mature mixed forest. Near Lisaku, Estonia. April 2018. Model released.

Nick Upton / Nest box for Siberian flying squirrel (Pteromys volans) in mature mixed forest. Muraka Forest Reseve, near Lisaku, Estonia. April 2018.

Nick Upton / Lisaku Park Forest from above, a mix of mature Fir (Abies sp) trees, Birch (Betula sp) and Eurasian aspen (Populus tremula). Forest host to Siberian flying squirrel (Pteromys volans). Estonia, April 2...

Nick Upton / Researchers fitting Siberian flying squirrel (Pteromys volans) nest box to tree. Mature mixed forest, Estonia. April 2018. Model released.

Nick Upton / Researchers fitting Siberian flying squirrel (Pteromys volans) nest box to mature tree and recording position on GPS unit. Estonia. April 2018. Model released.

Nick Upton / Forester hanging Siberian flying squirrel (Pteromys volans) nest box in mature mixed forest, Estonia. April 2018. Model released.

Nick Upton / Researcher radio tracking radio collared Siberian flying squirrel (Pteromys volans). Mature mixed forest, Muraka Forest Reseve, near Lisaku, Estonia. April 2018. Model released.

Nick Upton / Lisaku Park Forest from above, a mix of mature Fir (Abies sp) trees, Birch (Betula sp) and Eurasian aspen (Populus tremula). Forest host to Siberian flying squirrel (Pteromys volans). Estonia, April 2...

Nick Upton / Researcher reviewing trailcam footage on laptop of Siberian flying squirrel (Pteromys volans) emerging from nest hole in Aspen (Populus tremula) tree at night. Mature mixed forest, near Lisaku, Estoni...

Nick Upton / Siberian flying squirrel (Pteromys volans) fitted with radiocollar on Aspen (Populus tremula) trunk near nest hole. Mature mixed forest, near Lisaku, Estonia. April 2018.

Nick Upton / Siberian flying squirrel (Pteromys volans) entering nest hole in Downy birch (Betula pubescens) tree trunk. Mature mixed forest, near Lisaku, Ida Virumaa, Estonia. April.

Nick Upton / Siberian flying squirrel (Pteromys volans) peering out of nest hole in old Aspen (Populus tremula) tree. Mature mixed forest, near Lisaku, Estonia. April.

Markus Varesvuo / Pine grosbeak (Pinicola enucleator) mature male on rowan tree with snow covered berries, Liminka, Finland, January.

Markus Varesvuo / Pine grosbeak (Pinicola enucleator) mature male on rowan tree with snow covered berries, Liminka, Finland, January.

Markus Varesvuo / Pine grosbeak (Pinicola enucleator) mature male, on rowan tree with snow covered berries, Liminka, Finland, January

Markus Varesvuo / Pine grosbeak (Pinicola enucleator) mature male feeding on rowan tree with snow covered berries, Liminka, Finland, January

Laurie Campbell / Beech (Fagus sylvatica) mature tree in winter, Paxton House Estate, Berwickshire, Scotland, December

SCOTLAND: The Big Picture / Scots pine (Pinus sylvestris) saplings and mature tree in Abernethy Forest, Abernethy National Nature Reserve, Cairngorms National Park, Scotland, UK, June

SCOTLAND: The Big Picture / Scots pine (Pinus sylvestris), mature tree and saplings growing outside of deer fence marked with anti-collision tape for grouse, Kinveachy, Carrbridge, Cairngorms National Park, Scotland, June

SCOTLAND: The Big Picture / Mature Scots pine (Pinus sylvestris) surrounded by saplings in flowering heather moorland, Cairngorms National Park, Scotland, UK, August 2016.

SCOTLAND: The Big Picture / Mature Scots pine (Pinus sylvestris) surrounded by saplings in flowering heather moorland, Cairngorms National Park, Scotland, UK, August 2016.

Colin Varndell / Fruiting body of Giant polypore (Meripilus giganteus) fungus growing at the base of a mature beech tree. Dorset, UK October.

Sam Hobson / Lesser spotted woodpecker (Dryobates minor) male excavating nest hole in mature apple tree in ancient orchard. Herefordshire, UK. June

Sam Hobson / Lesser spotted woodpecker (Dryobates minor) male excavating nest hole in mature apple tree in ancient orchard. Herefordshire, UK. June

Nick Upton / Mature, pollen-producing male cones of a Canary island pine (Pinus canariensis), endemic to the Canaries, Teide National Park, Tenerife, Canary Islands, May.

Nick Upton / Mature, pollen-producing male cones of a Canary island pine (Pinus canariensis), endemic to the Canaries, Teide National Park, Tenerife, Canary Islands, May.

Nick Upton / Mature, pollen-producing male cone and old open female cone of a Canary island pine (Pinus canariensis), endemic to the Canaries, Teide National Park, Tenerife, Canary Islands, May.

Nick Upton / Developing and mature open cone of Turkish pine (Pinus brutia), Kilada, Argolis, Peloponnese, Greece, August 2013.

Nick Upton / Mature, open cone of Turkish pine (Pinus brutia), Kilada, Argolis, Peloponnese, Greece, August 2013.

Alex Hyde / Lichen (Lobaria virens) with mature apothecia (or fruiting body) growing on a sycamore tree trunk. Isle of Mull, Scotland, UK. June.

Alex Hyde / Lichen (Lobaria virens) with mature apothecia (or fruiting bodies) growing on a sycamore tree trunk. Isle of Mull, Scotland, UK. June.

Alex Hyde / Lichen (Lobaria virens) with mature apothecia (or fruiting body) growing on a sycamore tree trunk. Isle of Mull, Scotland, UK. June.

Colin Varndell / Detail of bark texture on mature Horse chestnut (Aesculus hippocastanum) tree in field near Upton Country Park, Dorset, UK, May.

Alex Hyde / Bark of mature Field maple (Acer campestre). Cambridgeshire, UK, September.

Alex Hyde / Wych Elm (Ulmus glabra) bark on a mature tree. Peak District National Park, Derbyshire, UK. May.

Alex Hyde / Tree lungwort (Lobaria pulmonaria) lichen growing on a mature beech tree. Kyle of Lochalsh, Scotland. March.

Alex Hyde / Tree lungwort (Lobaria pulmonaria) lichen growing on a mature beech tree. Kyle of Lochalsh, Scotland. March.

Alex Hyde / Tree lungwort (Lobaria pulmonaria) lichen growing on a mature beech tree. Kyle of Lochalsh, Scotland. March.

Alex Hyde / Tree lungwort (Lobaria pulmonaria) lichen growing on a mature beech tree. Kyle of Lochalsh, Scotland. March.

Mary McDonald / Pale chanting goshawk (Melierax canorus) adult feeding juvenile, Samburu Game Reserve, Kenya, Africa, November.

Mary McDonald / Pale chanting goshawk (Melierax canorus) feeding on lizard, Samburu Game Reserve, Kenya, Africa, November.

Kevin Schafer / Japanese Cedar (Cryptomeria japonica), Shiratani Unsuikyo, Kirishima-Yaku National Park, Yakushima Island, Japan

Anup Shah / Tana red colobus (Procolobus rufomitratus) mature female eating leaves in a tree. Tana River Forest, South eastern Kenya.

Anup Shah / Tana red colobus (Procolobus rufomitratus) mature female eating leaves in a tree. Tana River Forest, South eastern Kenya.

Fiona Rogers / Yellow baboon (Papio cynocephalus) mature male sitting against a tree. Tana River Forest, South eastern Kenya.

Fiona Rogers / Yellow baboon (Papio cynocephalus) mature male sitting against a tree. Tana River Forest, South eastern Kenya.

Colin Varndell / Mature Beech tree (Fagus Sylvatica) in late spring, Dorset, UK, May.

John Waters / Close planted row of mature Beech trees (Fagus sylvatica) along trackway on the Mendip Hills above Draycott, Somerset, UK, February 2014. Digital composite.

John Waters / Close planted row of mature Beech trees (Fagus sylvatica) along trackway on the Mendip Hills above Draycott, Somerset, UK, February 2014. Digital composite.

Colin Varndell / Mature Beech (Fagus sylvatica) trees in Mark Ash Wood, New Forest, Hampshire, UK, November.

Alex Hyde / Sycamore bark (Acer pseudoplatanus) on a mature tree. Peak District National Park, Derbshire, UK. April.

George Sanker / Mature grizzly bear (Ursus arctos horribilis) in early morning snowfall, Yellowstone National Park, Wyoming, USA, June.

John Waters / Mature beech trees (Fagus sylvatica) growing out of moss-covered stone wall near Ilfracombe, Devon, December.

John Waters / Mature beech trees (Fagus sylvatica) growing out of moss-covered stone wall near Ilfracombe, Devon, December.

Fiona Rogers / Eastern Black-and-white Colobus (Colobus guereza) female with baby aged 2-3 months sitting with mature male in a tree. Kakamega Forest South, Western Province, Kenya

George Sanker / Bull Elk (Cervus elaphus), mature bull thrashing a small tree during the mating season. Jasper National Park, Alberta, Canada, September

Kevin Schafer / Giant Sequoia (Sequoiadendron giganteum) tree, Sequoia National Park, California

Alex Hyde / Honey Fungus (Armillaria mellea) growing on mature Ash tree (Fraxinus excelsior). Peak District National Park, Derbyshire, UK. September.

Alex Hyde / Honey Fungus (Armillaria mellea) growing on mature Ash tree (Fraxinus excelsior). Peak District National Park, Derbyshire, UK. September.

Anup Shah / Sumatran orangutan (Pongo abelii) mature male 'Halik' aged 26 years seated with female 'Juni' aged 12 years swinging from a tree in the background - wide angle perspective. Gunung Leuser National Park...

Anup Shah / Sumatran orangutan (Pongo abelii) mature male 'Halik' aged 26 years peering from behind a tree. Gunung Leuser National Park, Sumatra, Indonesia. Rehabilitated and released (or descended from those whi...

Anup Shah / Sumatran orangutan (Pongo abelii) mature male 'Halik' aged 26 years resting in a tree. Gunung Leuser National Park, Sumatra, Indonesia. Rehabilitated and released (or descended from those which were r...

Cyril Ruoso / Japanese Cedar (Cryptomeria japonica), Jomon Sugi, the oldest and largest of its kind is at least two thousand years old, Yakushima Island, Japan

Cyril Ruoso / Til (Ocotea foetens) tree, a one century old specimen, Madeira