habitat loss Flashcards
what is habitat loss
when a natural habitat is converted to a human dominated habitat
= greatest threat to biodiversity and responsible for nealry 50% of declines in species
refers to complete elimanation of habitats along with bio communities and eco functions
how does habitat loss happen
DeFries came up with a predictable sequence of events which occurs but the timescale varies in different areas
1) presettlement = natural ecosystems, occured 5000 years ago
2) frontier- clearings
3) subsistence = agricultural and small scale farms bronze age
4) intensifying= intensive agriculture
5) intensive = urban areas and protected recreational lands where we are currenlty
= stages of land use transition
how is agriculture a primary driver to habitat loss
between 1700 and 1950s agricultural land increaed by 450% and currently 40% of land surface
what was the green revolution
1930-1960 a period of tech transfer initatives that saw greatly increased crop yeilds avoding mass starvation but leading to intensification and expansion of agriculture
how can be feed a rising population
1) increase agricultural land but will reduce natural habitats
2) increase crop yeilds- may lead to increase pollution and more habitat destruction
3) change in diets and avoid waste- meat and dairy require more land and enegry
how is urbanisation a primary driver for habitat loss
currently 3% of land and predicted to increase 9%
- 7/10 people will be living in megacities by 2050
- intense urbanisation leads to 55% loss of biodiversity and close to 80% in some cases
how can urbanisation occur whilst maintaining biodiversity
urban planning and design as well as use of green infrastructure
engineering cities to enhance biodiversity and ecosystem services
1) provide urban green spaces e.g. lumpini park in bangkok
2) green infrastructure which offers more habitat for flora fauna than physical infrastructure e.g. natural wetland and water courses rather than pipelines used for drainage
3) green architecture e.g. two residential towers in italy serve as a migratory habitat fir birds and insects
what did Beninde et al 2015 find when looking at biodiversity and urban habitats
biodiversity increases when urban habitats
1) have more green space
2) more habitat types
3) more plant cover
4) less intensly managed
5) contain water
how are extractive industries a prime driver for habitat loss
those that remove raw material from nature such as gas extraction, mining and quarrying
causes other issues as well such as pollution
thought to caused around 7% deforestation in subtropics, loss of 30,000 square km in north america to oil drilling
how can aquaculture be a primary driver to habitat loss
fast growing area now producing over half seafoods
has advanatges but also destroys habitats
e.g. half mangroves lost and 40% endemic verterbrates threatened
magroves important breeding and feeding grounds for fish and shellfish as well as costal protection from storms and tsunamis
where is habitat loss happening
some biomes have been more affected than others
forests average 50% loss over 5000 yrs with most temperate forest already lost
highest in tropics moslty due to practises established during colonialism such as mechanized logging of forest reserves and mining
grasslands= suitability to agriculture led to destruction of many natural grasslands
coral reefs- provide food and resources for over 500 million people but massive decline 25% behonde repair and 90% projected to be in danger= main risk is coral belaching, overfishing and pollution
what is rewilding
enabling natural processes to shape land and sea e.g. few chemicals and fertilisers used, creating space in landscape for seeds to grwo, grazing animals allowing new shoots , their dung acting as natural fertiliser
what is meant by land sharing vs land sparing
is it better to use larger proportion of land at lower intesnity or small piece of land at higher intensity thus sparing some from development
sharing - argue that best way to conserve biodiversity is to integrate patcges of natural habitat into landscapes characterised by small scale farms with low intensity land use practises
sparing - argues best way is to set aside large areas as national parks that are seperated from damaging human activites and intesnfy production at expense of natural habitat
what are the different types of farming
conventional- large feilds of monocultures managed with heavy machenergy and synthetic fertilisers
organic- low input small scale diverse farms certified organic farming prohibits synthetic inputs but allowing organic
sustainability intensified farming= incroporates agroforestry, conservation agriculture and bio pest control produce low input
diversified farming- integrates several crops or animals in production system to promote agrobiodiversity and ecosystem services reducing need for external input
agroecologcial = emphasises integration of farms into surrounding landscape that conserves and manage biodiversity to support crop production bio pest control and pollination
why is land sparing thought to be more beneficial for conservation
found species more negativley impacted by agriculture than benefited form it when they used more land but removed more natural habitats
land sparing more promising stratergy for minimising negative impacts of food production as most species are highly adapted to a niche so land sharing causes fragmentation and degradation that damages these niches
= Phalan et al 2011
