Bryan and Cherry Alexander / Pumping unit in the oil fields near Niznevartovsk. Khanty Mansiysk, Western Siberia, Russia, 2000.

Michael Durham / Western Pipistrelle (Pipistrellus hesperus) bat flying over desert scrub, near Pine Creek in the John Day Fossil Beds National Monument, Clarno Unit, Oregon, this is the smallest bat found north of Me...

Michael Durham / Western Pipistrelle (Pipistrellus hesperus) bat chases a moth over desert scrub, near Pine Creek in the John Day Fossil Beds National Monument, Clarno Unit, Oregon

David Tipling / Officer from the British Sovereign Base Area Police anti trapping unit at Dekeleia holds a Blackcap (Sylvia atricapilla) rescued from an illegal trappers mist nest in Cyprus, September 2011

David Tipling / Officer from the British Sovereign Base Area Police anti trapping unit at Dekeleia holding a Blackcap (Sylvia atricapilla) rescued from a trappers mist nest in Cyprus, September 2011

David Tipling / Officers from the British Sovereign Base Area Police anti trapping unit at Dekeleia extracting a Blackcap (Sylvia atricapilla) from an illegal trappers mist nest in Cyprus, September 2011

Gary K. Smith / Milk tanker filling up at small dairy unit, Binham Village, Norfolk, UK

Mark Carwardine / Takahe (Porphyrio mantelli) Burwood Bush Takahe Rearing Unit, near Te Anua, New Zealand, Endangered species

Mark Carwardine / Takahe (Phorphyrio hochstetteri) Burwood Bush Takahe Rearing Unit, near Te Anua, New Zealand, Endangered species

Mark Carwardine / Takahe (Phorphyrio hochstetteri) Burwood Bush Takahe Rearing Unit, near Te Anua, New Zealand Endangered species

Christophe Courteau / West African giraffe {Giraffa camelopardis peralta} poached by local people. Sahel, Niger. Anti-poaching unit investigates carcass; meat will be donated to villagers

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-r Eric Moletshe, Michael Duplessis, Louis Ngubene, Abre Marais, Protrack anti-poaching unit, Hoedspruit, Limpopo, South Africa, June 2012. Editorial use onl...

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-r Mshiyeni Ntuli, Sibongiseni Kunene, Sibusiso Mdluli, Ezemvelo KZN Wildlife, iMfolozi game reserve, KwaZulu-Natal, South Africa, June 2012. Editorial use o...

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-r Sibongiseni Kunene, Mshiyeni Ntuli, Sibusiso Mdluli, Ezemvelo KZN Wildlife, iMfolozi game reserve, KwaZulu-Natal, South Africa, June 2012. Editorial use o...

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-r Mshiyeni Ntuli, Sibongiseni Kunene, Sibusiso Mdluli, Ezemvelo KZN Wildlife, iMfolozi game reserve, KwaZulu-Natal, South Africa, June 2012. Editorial use o...

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-r Abre Marais, Eric Moletshe, Protrack anti-poaching unit, Hoedspruit, South Africa, June 2012. Editorial use only

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, l-rSibusiso Mdluli, Sibongiseni Kunene, Ezemvelo KZN Wildlife, iMfolozi game reserve, KwaZulu-Natal, South Africa, June 2012. Editorial use only

Ann & Steve Toon / Anti-poaching unit on patrol in the bush, led by Sibongiseni Kunene, Ezemvelo KZN Wildlife, iMfolozi game reserve, KwaZulu-Natal, South Africa, June 2012. Editorial use only

Ernie Janes / Looking across countryside to villages of Cley and Wiveton from Wiveton Downs, North Norfolk, UK, April 2012. Free-range pig unit in foreground and sea in distance,

Ernie Janes / Domestic pig (Sus scrofa domestica) free-range rearing unit in spring at Glandford from Wiveton Downs, Norfolk, April, 2012.

Merryn Thomas / Cornish Pilot Gigs pulled up on Town Beach, St. Mary's, Isles of Scilly. World Pilot Gig Championships, May 2009.

JEFF FOOTT / Skins of poached animals - tiger, snake, leopard -confiscated by the Rhino Protection Unit in Tikoli, near Chitwan NP, Nepal, 2003

Florian Möllers / Member of the Snare Removal Unit at Budongo Conservation Field Station removes snare set for duikers and bush pig that could seriously harm or mutilate chimpanzees which might accidentially get caug...

Florian Möllers / Moses Lemi of the Snare Removal Unit at Budongo Conservation Field Station remove snares that could seriously harm or mutilate chimpanzees which might accidentially get caught in them. Budongo Forest...

Mike Salisbury / Camerawoman Justine Evans filming presenter Sir David Attenborough in a canopy crane on location for BBC Natural History Unit series 'Life of Birds'. Venezuela, 1997

John Cancalosi / Mobile Surveillance Unit vehicle, U.S. Border Patrol, Huachuca Mountains, Arizona, USA. Uses radar-infrared technology and a video camera to monitor United States and Mexican border

John Cancalosi / Mobile Surveillance Unit vehicle, U.S. Border Patrol, Huachuca Mountains, Arizona, USA. Uses radar-infrared technology and a video camera to monitor United States and Mexican border

Suzi Eszterhas / Mara Conservancy Rangers (Anti-poaching unit) removing snares from bushes, Masai Mara Conservancy, Kenya, August 2006

Suzi Eszterhas / Mara Conservancy Rangers (Anti-poaching unit) removing snares from bushes, Masai Mara Conservancy, Kenya, August 2006

Tim Laman / Self portrait of Photographer, Tim Laman, climbing an emergent mahogany tree in the Gran Caldera Volcanica de Luba, Bioko Island, Equatorial Guinea, Rapid Assessment Visual Unit, International League...

Jerry Monkman / Piping plover {Charadrius melodus} Long Beach, Stratford, Connecticut, USA. Adjacent to the Great Meadows Unit of McKinney National Wildlife Refuge.

Jerry Monkman / Piping plover nest {Charadrius melodus} with four eggs on sand, Long Beach, Stratford, Connecticut, USA. Adjacent to the Great Meadows Unit of McKinney National Wildlife Refuge.

Stephen Belcher / Rhino protection unit officer holding wire snare that poachers use to trap rhinos, Way Kambas National Park, Sumatra, Indonesia

Adrian Davies / Mobile Air quality monitoring unit beside a road in Richmond, London, UK

Kirkendall-Spring / Spires near Cedar Pass in the North Unit of Badlands National Park, South Dakota, USA.

Kirkendall-Spring / Spires of rock and mudstone along the Castle Trail in the North Unit of Badlands National Park, South Dakota, USA.

Tim Fitzharris / Badlands, South Unit, Theodore Roosevelt National Park, North Dakota

Rob Cousins / Alastair Fothergill, Producer and ex Head of the BBC Natural History Unit, Bristol, UK 1996

Jack Dykinga / Saguaro Cacti (Carnegiea gigantea) silhouetted at sunset in the Tucson Mountains West unit, Saguaro NP, Arizona, USA

Ben Osborne / Woman putting plastic bottle into recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK 2007 model released

Ben Osborne / Woman putting plastic bottle into recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK

Ben Osborne / Woman putting aluminium can into recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK, 2007 model released

Ben Osborne / Woman putting aluminium can into recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK 2007 model released

Ben Osborne / Shoe recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK

Ben Osborne / Woman putting glass bottle into recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK, 2007 model released

Ben Osborne / Shoe recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK

Ben Osborne / Oxfam Clothing and shoe recycling unit in supermarket carpark, Shrewsbury, Shropshire, UK

Pete Oxford / String of braided tabacco leaves. Tabacco is sold by unit length, then dried and hand rolled. Antandroy market at Faux Cap, Southern MADAGASCAR. 2005

BBC COPYRIGHT / Producer Alastair Fothergill, as Head of BBC Natural History Unit in 1996

Michael Durham / Western Pipistrelle (Pipistrellus hesperus) in the John Day Fossil Beds National Monument, Clarno Unit, Oregon. This is the smallest bat found north of Mexico

Michael Durham / Deer Mouse (Peromyscus maniculatus) under a juniper tree at night, John Day Fossil Beds National Monument, Clarno Unit, Oregon

John Downer / Alan Hayward filming in macro studio for "Galactic Gardens" Bristol Natural History Unit, 1985

Michael Durham / Townsend's Big-eared Bat (Corynorhinus townsendii) flying at night, John Day Fossil Beds National Monument, Clarno Unit, Oregon

Michael Durham / Townsend's Big-eared Bat (Corynorhinus townsendii) male roosting on a rock, John Day Fossil Beds National Monument, Clarno Unit, Oregon

Michael Durham / Hoary Bat (Lasiurus cinereus) male flying at night, near pine creek in the John Day Fossil Beds National Monument, Clarno Unit, Oregon

Michael Durham / Hoary Bat (Lasiurus cinereus) male flying at night, near pine creek in the John Day Fossil Beds National Monument, Clarno Unit, Oregon

Tim Fitzharris / Sedimentary formation in the Painted Hills unit of John Day Fossil Beds National Monument, Oregon

Tim Fitzharris / Desert vegetation in the Painted Hills unit of John Day Fossil Beds National Monument, Oregon

George McCarthy / Domestic pigs {Sus scrofa domestica} Gloucester Old Spot with piglets, Free range rearing Unit, Norfolk, UK

Jabruson / Camel anti-poaching unit on patrol, Meru NP, Kenya

Gary Smith / Domestic Pigs {Sus scrofa domestica} in fattening unit, Norfolk, UK.

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) family band forms solid unit during summer breeding season, Pryor Mountain Wild Horse Range, Montana

Dan Rees / The Sphinx, Cairo, Egypt with BBC NHU film unit

Doug Allan / Doug Allan, BBC Natural History Unit cameraman without wetsuit, but with beard and camera. Antarctic, 1985. Antarctica

Mike Read / Portuguese Fireplace, memorial to a Portuguese army unit that helped to produce timber for the war effort during the First World War, New Forest National Park, Hampshire, UK, February 2009

Stephen Belcher / Sticker of the Indonesian Rhino Conservation Program at the Rhino Protection Unit headquarters, Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel patrolling in Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel entering Way Kambas National Park at the beginning of a patrol, Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel entering Way Kambas National Park by boat, Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit personnel on vehicle entering Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Rhino protection unit officer holding poached sumatran rhino skull and pointing to bullet hole, Way Kambas National Park, Sumatra, Indonesia

Stephen Belcher / Sign at entrance to the Sumatran Rhino Protection Unit, Way Kambas National Park, Sumatra, Indonesia

Jim Brandenburg / Senior warden Ted Goss of Department of Wildlife and Conservation, Rhinoceros Anti-poaching Unit, with his rangers many of whom are former poachers, Kenya