Human impact on biodiversity Snow leopard Panthera uncia

What are the human activities that are causing a loss of biodiversity? • •

Over exploitation • Over hunting • Over fishing • Clear felling forests BBC Clear felling in the Amazon forest Mongabay. com American bison skulls waiting to be ground for fertiliser (1870) © 2016 Paul Billiet ODWS

The passenger pigeon (Ectopistes migratorius) © 2016 Paul Billiet ODWS Songbird foundation

The passenger pigeon (Ectopistes migratorius) • • Estimated population early 1800 s 3 to 5 billion Extinct in 1914 Reason: Excessive over hunting The arrival of railways and the telegraph during the period 1860 -1890 increased the mobility and co-ordination of the hunters. © 2016 Paul Billiet ODWS

Enter the realm of the living dead • 1895 a single flock remained of an estimated 250 000 birds • A hunt in April 1895 killed 200 000 and maimed 40 000 About 5 000 escaped • The population was below the point where it could recover. © 2016 Paul Billiet ODWS Hunting passenger pigeons

The last survivor • By 1912 the last male bird died in captivity •

Islandisation • Dividing and isolating populations of species so that they cannot breed together

Habitat destruction • The total loss of an organism’s habitat will lead to its extinction • Tropical forests are disappearing at a rate of 76 000 km 2 per year • This results in the estimated loss of 4000 to 6000 species per year. © 2016 Paul Billiet ODWS NASA earth observatory

Pollution • E. g. plastic bags are killing marine turtles that mistake them for jellyfish, their natural food • Displacement of ecosystems due to global warming • If species (e. g. trees) cannot disperse fast enough they will become extinct. © 2016 Paul Billiet ODWS NOAA Coris

Introduction of alien species • Species introduced accidentally (e. g. rats) • Species introduced deliberately (e. g. foxes in Australia) • These will increase in numbers and out compete or heavily predate native species • The aliens have little or no natural predators to control them • Kiwis v rats and cats in NZ. © 2016 Paul Billiet ODWS Invasive animals cooperative research centre

European starling (Sturnus vulgaris) • Between 1890 and 1891, 160 of these birds were released in Central Park New York. • By 1942 they had spread as far as California. • An estimate population of between 140 and 200 million starlings now exist in North America • One of the commonest species of bird on Earth © 2016 Paul Billiet ODWS

European starling (Sturnus vulgaris) Current distribution CJKrebs (1978) Ecology © 2016 Paul Billiet ODWS

The Colorado Beetle (Leptinotarsa decemlineata) • A potato pest from North America • It

The Colorado Beetle (Leptinotarsa decemlineata) Begon, Townsend & Harper (1990) Ecology © 2016 Paul

Biological pest control • • Control of pest species using the natural predators No

Prickly pear cactus (Opuntia stricta) • Native of N and S america • 1839 Introduced into Australia planted as hedges • The population got out of control • 1880 classified as a pest. © 2016 Paul Billiet ODWS

The invasion spreads © 2016 Paul Billiet ODWS Year Area invaded / ha 1900

Biological control agent Cactoblastis cactorum • 1920 Search in the prickly pear’s native habitats found 50 insect species that eat it • 12 were released in Australia • One species was effective at controlling it, the moth Cactoblastis cactorum from Argentina. Larva Cactoblastis Adult moth © 2016 Paul Billiet ODWS

A success story • Complete control of the cactus achieved by 1940 • Today the cactus is found locally distributed • As soon as its numbers increase the moth population increases and the cactus is brought under control. © 2016 Paul Billiet ODWS