Humans and the rain forestlecture 5

25.2.2019

Chris J Kettle

Living in the “Anthropocene”

Extinctions and humans• Over the last 50,000 years

extinction of large mammals has been relatively common loosing as many as 90 genera (why?)

• The earliest extinction due to humans was 11K years ago (late pleistocene) largely through hunting and fire. Ground sloths and Gomphotheres

• Americas experienced major extinction wave of 70-80% of large mammals, associated with the ‘Clovis hunters’

Holocene extinctions

• African forest seen less extinctions

• Indonesian Island of Java seen loss of many large mammals in last 2600 years

• Oceanic islands have been especially vulnerable to human driven extinctions

Human migration

• As humans moved eastward across the Pacific some 2000 bird species became extinct.

• Wave of extinctions on Madagascar shortly after humans arrived circa 2000 BP

• Driven by introductions, disease and habitat loss and fire

• The dodo Raphus cucullatus

Collapse of the world’s largest herbivores

Ripple et al 2015 Science Advances

60% of large herbivores threatened

Prehistoric legacies

Willis et al. 2004. How “virgin” is virgin rainforest. Science 304, 402

Human impacts are not completely irreversible…

… scope for developing strategies for enhancing resilience and resistance to impacts, which would aid in later recovery

Human legacies

• Only the rain forests of Australia seem to have been uninhabited

• human habitation considerable impact on the forest

• Agricultural long history in the wet tropics with selective pressures on plant species

Palaeohuman settlements

• Large scale landscape transformation in the Amazon altered forest composition and soil 6-12 people per Km2

Humans and Fire• Radio carbon dating demonstrate the

expansion of agriculture with peaks.

• This was followed by a period of abandonment

• Subsequent collapse of American indigenous communities (1500 AD) was followed by regeneration of dense forests.

• Many forest areas of the Amazon are better described as human created

European expansion

• Calamitous collapse of indigenous societies

• Changes in forest legislation to suit colonial timber exploitation

• New systems of land management and “scientific” resource use had a lasting legacy on forest management

• Slavery and disregard for indigenous lives

Hevea brasiliensis

Palaquium gutta

Cinchona

Kuda-kuda log hauling method.

Log raft

Industrial deforestation

• Broadly caused by agricultural expansion

• Patterns, causes and extent differ across the main tropical regions

• Much of Amazon, SE Asia and Africa were intact until the 1970’s, Mesoamerica and South Asia had already experienced widespread fragmentation

The future of forests

In 1<50% in 150

years

= 400

Crowther et al. 2015 Nature

Transitions of deforestation

Drivers of deforestation

Accelerated forest loss

• Since the 1970’s there has been a dramatic increase in rates of deforestation across the tropics.

• Forest conversion and degradation

• 130,000 km2 of the worlds forest lost annually 55,000 km2

of primary tropical forest

Drivers of deforestation

Deforestation in Brazil• Reflects much of

central and south America

• 2/3’s of the Amazon and all tropical Atlantic rain forest are in Brazil

• Early colonisation of the Atlantic costal forest

• Later, Operation Amazonia 1964-1967

Deforestation in Asia• Government sponsored

forest development schemes especially in Indonesia and Malaysia

• Transmigration of people from densely populated island; ITP officially resettled approx. 5 million people (10 -15 million others)

Lukas Straumann, Bruno Manser Fonds, www.money-logging.org

Sarawak, Malaysia‘s largest state

Conversion des forêts en plantations...

Conversion des forêts en plantations...

.

Mining

• Gold, silver, copper, aluminium and other precious metals.

• Associated with major road construction.

• Pollution related to processing (mecury and cyanide for gold)

Conclusion

• No Tropical rainforest remain untouched by humans

• Past history demonstrates the resilience of tropical forests

• Humans have had and continue to have significant and irreversible impacts on tropical forests, often involving huge sums of money

• Many of these processes may be synergistic, such as fragmentation, fire and climate change.