AMAZON RAINFOREST

Key points for the water cycle/temps in the Amazon?

• High average temps = response to intense insolation throughout year.

• However, significant cloud cover ensures that max. temps do not reach the extremes of sub-tropical desert climates.

• Seasonal differences in temps are small & convectional rain falls all year round, though most areas experience at least one drier period.

Flows/Processes & water cycle in Amazon?

• 50-60% of precipitation in Amazonia is recycled by evapotranspiration.

• Water losses from Amazon Basin result from river flow & export of atmospheric vapour to other regions.

• This loss is made good by inward flux of moisture from the Atlantic Ocean.

Precipitation? (5 points)

• High average rainfall = >2000mm.

• Rainfall fairly evenly distributed throughout the year though short, drier season occurs in somes places.

• High-intensity, convectional rainfall.

• Interception by forest trees is high – around 10% of precipitation.

• Intercepted rainfall accounts for 20-25% of all evaporation.

Evapotranspiration? (4 points)

• High rates due to high temps, abundant moisture & dense vegetation.

• Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals.

• Around 50% of incoming rainfall is returned to atmosphere by evapotranspiration.

• Most evaporation is from intercepted moisture from leaf surfaces – moisture lost in transpiration is derived from soil via tree roots.

Run-off? (2 points)

• Rapid run-off related to high rainfall, intensive rainfall events & well-drained soils.

• Depending on seasonal distribution of rainfall, river discharge may peak in 1 or 2 months of the year.

Atmosphere (water cycle)? (3 points)

• High temps allow atmosphere to store large amounts of moisture.

• Absolute humidity is high.

• Relative humidity is low.

Soil/groundwater?

Abundant rainfall & deep tropical soils lead to significant water storage in soils & aquifers.

Vegetation?

Rainforest trees play crucial role in water cycle, absorbing & storing water from the soil & releasing it through transpiration.

Key carbon cycle figures? (4 points)

• Rainforest = major global reservoir of stored carbon, absorbing 2.4 billion tonnes/year.

• NPP is high – averaging 2500 grams/m²/year & the biomass is 400-700 tonnes/ha.

• Large forest trees typically store around 180 tonnes C/ha and 40 tonnes C/ha in their roots.

• Soil carbon stores = 90-200 tonnes/ha.

Carbon cycle? (4 points)

• Exchanges of carbon between atmosphere, biosphere & soil = rapid.

• High humid equatorial climate - ideal conditions for plant growth.

• Warm, humid conditions = speedy decomposition of dead organic matter & quick release of CO₂.

• Rates of carbon fixation through photosynthesis = high.

Soils/carbon in Amazon? (2)

• Leached & acidic soils contain limited carbon & nutrient stores.

• Poor soils support a biome with highest NPP & biomass of all terrestrial ecosystems - shows speed which organic matter is broken down, mineralised & recycled.

How does geology affect the water cycle? (3 points)

• Impermeable catchments e.g. large parts of Amazon Basin are an ancient shield area comprising impermeable, crystalline rocks – have minimal water storage capacity.

• This results in rapid run-off.

• Permeable porous rocks e.g. limestones & sandstones store rainwater & slow run-off.

How does relief affect the water cycle? (5 points)

• Most of Amazon Basin comprises extensive lowlands.

• In areas of gentle relief, water moves across the surface as overland flow, or horizontally through the soil as throughflow, to streams/rivers.

• West = Andes, creates steep catchments with rapid run-off.

• Widespread inundation across extensive floodplains e.g. the Pantanal, occurs annually.

• This stores water for several months & slowing its movement into rivers.

How does temperature affect the water cycle? (3 points)

• High temps throughout year generate high rates of evapotranspiration.

• Convection is strong, leading to high atmospheric humidity, the development of thunderstorm clouds & intense precipitation.

• Water is cycled continually between the land surface, forest trees & atmosphere by evaporation, transpiration & precipitation.

Key stores/flows in the carbon cycle? (5 points)

• Forest trees dominate biomass of Amazon Basin & are principal carbon store.

• Approx. 100 billion tonnes of carbon is locked in Amazon rainforest.

• Absorbing around 2.4 billion tonnes of CO2/year & releasing 1.7 billion tonnes through decomposition – rainforest is a carbon sink of global importance.

• 60% of rainforest carbon is stored in above ground biomass of tree stems, branches & leave – remainder is below ground (roots & soil organic matter).

• Carbon cycles between forest & other living organisms, the soil & atmosphere.

How does NPP affect the carbon cycle? (5 points)

• Photosynthesis connects the rainforest to the atmosphere carbon stores.

• High temps, high rainfall & intense sunlight stimulate primary production.

• NPP averages about 2500 gams/m2/year.

• Amazonia alone accounts for 15-25% of all NPP in terrestrial ecosystems.

• Leaf litter & other dead organic matter accumulates temporarily in the soil surface & within rainforest soils.

How does decomposition affect the carbon cycle? (2 points)

• High temps & humid conditions promote rapid decomposition of organic litter by bacteria, fungi & other soil organisms.

• Decomposition releases nutrients to the soil for immediate take-up by tree root systems & emits CO2 which is returned to the atmosphere.

How does geology affect the carbon cycle?

• Geology = dominated by ancient igneous & metamorphic rocks – carbonates are largely absent from mineral composition.

• However, in western parts of basin close to Andes, outcrops of limestone occur – significant regional carbon stores (slow-carbon cycle).

How has human factors affecting the water cycle changed over time? (3 points)

• 1970-2013: Deforestation averaged around 17,500 km2/year.

• Since 1970, almost 1/5 of primary forest has been destroyed/degraded.

• Since 2009 annual rates have been lower than the average but have started to rise again in recent years.

How did the floods in Madeira River affect the water cycle? (4 points)

• April 2014 = devastating floods occurred on Madeira River – largest tributary of Amazon River.

• Porto Velho: rover reached record levels of 19.68m above normal.

• Vast expanses of floodplain were inundated – 60 people died; 68,000 families were evacuated & there were outbreaks of cholera & leptospirosis.

• Upper Madeira drainage basin – human activity has modified stores & flows in the water cycle.

How has deforestation affected the water cycle? (3 points)

• Deforestation has reduced water storage in forest trees, soils (that have been eroded), permeable rocks (more rapid run-off) and the atmosphere.

• At the same time fewer trees mean less evapotranspiration, therefore less precipitation.

• Total run-off and run-off speeds have increased – raising flood risks throughout the basin.

Deforestation linked to Bolivia & Peru? (3)

• Despite torrential rains in upper basin of Madeira River, the main driver of the floods was deforestation in Bolivia & Peru.

• 2000-2012, 30,000 km2 of Bolivian rainforest was cleared for subsistence farming and cattle ranching.

• Much of this deforestation occurred on steep lower slopes of Andes – resulted in a massive reduction in water storage & accelerated run-off.

How has deforestation impacted the water cycle on a local scale? (6 points)

• Deforestation has hugely impacted the water cycle & has potential to change the climate at local & regional scales.

• Converting rainforest to grassland increases run-off by a factor of 27.

• 50% of rainfall on grassland does directly into rivers.

• Trees = crucial part of water cycle, extracting moisture from soil, intercepting rainfall & stabilising forest albedo & ground temps.

• Cycle sustains high atmospheric humidity - responsible for cloud formation & heavy convectional rainfall.

• Deforestation breaks this cycle & can lead to permanent climate change.

Regional impacts from deforestation on water cycle? (2 points)

• However, the impact of deforestation on water cycles is not just local – projections of future deforestation in Amazonia predict 20% decline in regional rainfall as rainforest dries out & forest trees are gradually replaced by grassland.

• Distribution of the regional water cycle means that forests hundreds of kms downwind of degraded sites are affected too.

Present day human factors affecting the carbon cycle? (3 points)

• Present-day deforestation is most severe in the tropical rainforest.

• In primary rainforest unaffected by human activity, the biomass of trees represents 60% of all the carbon in the ecosystem.

• Above ground carbon biomass in the rainforest is approx. 180 tonnes/ha – most remaining carbon is found in the soil as roots and dead organic material.

How does deforestation exhaust the carbon biomass store? (3 points)

• Croplands & pasture contain only small amount of carbon compared to forest trees.

• E.g. the biomass of grasslands in areas of former rainforest is 16.2 tonnes/ha, and for soya cultivation is just 2.7 tonnes/ha.

• Deforestation drastically reduces inputs of organic material into the soil – soils depleted of carbon & exposed to strong sunlight support fewer decomposer organisms, thus reducing the flow of carbon from the soil to the atmosphere.

How does deforestation affect the rainforest soils? (3 points)

• Rainforest soils contain only a small reservoir of essential nutrients and the forest is only sustained by a rapid nutrient cycle.

• Deforestation destroys the main nutrient store (forest trees) and removes most nutrients from the ecosystem.

• Nutrients no longer taken up by the root systems of tress are washed out of soils by rainwater & soils without the protective cover of trees are quickly eroded by run-off.

Management strategies international impacts on water and carbon cycles? (3 points)

• Degrading/destruction of large areas of Amazon rainforest is an issue of international as well as national concern.

• Deforestation has implications for global climate change.

• Brazil is committed to restoring 120,000km2 of rainforest by 2030.

Management strategies local impacts on water and carbon cycles? (3 points)

• Indigenous people have lived sustainable in the rainforest for thousands of years, maintaining the water balance, carbon cycle & the forest’s biodiversity.

• These people have survived as hunter-gatherers & shifting cultivators.

• Contrasting exploitative commercial farming, logging & mining of the past 50 years, indigenous people perused a way of life perfectly adapted to the limited resources & fragility of the rainforest.

What 3 categories do modern strategies to manage the Amazon fall into?

1. Protection through legislation of large expanses of primary forest so far unaffected by commercial developments.

2. Projects to reforest areas degraded or destroyed by subsistence farming, cattle ranching, logging or mining.

3. Improving agricultural techniques to make permanent cultivation possible.

What has the government done as management strategies? (3 points)

• Since 1998, the Brazilian government has established many forest conservation areas.

• These Amazon Regional Protected Areas now cover an area 20 times the size of Belgium.

• By 2015, 44% of the Brazilian Amazon comprised national parks, wildlife reserves and indigenous reserves where faming is banned.

What is the Reforestation Project: Parica Project? (4 points)

• Several projects sponsored by local authorities, NGOs and businesses, are underway but so far progress has been slow.

• E.g. the Parica Project in Rondônia in the western Amazon – sustainable forestry scheme aims to develop a 1000km2 commercial timber plantation on government-owned, deforested land.

• Plan is for the 20 million fast-growing, tropical hardwood seedlings, planted on 4000 smallholdings, to mature over a period of 25 years.

• Financial assistance is given to smallholders for land preparation, planting & maintenance of plots.

How does the Reforestation Project: Parica Project work? (4 points)

• Tree nurseries provide them with seedlings.

• Timber will be exported along the Amazon & its tributaries through Manaus or Port Velho.

• However, this project is monoculture & cannot replicate the biodiversity of the primary rainforest – BUT it is sustainable.

• It sequesters carbon in the trees & soil, reduces CO2 emissions from deforestation, re-establishes water & carbon cycles, reduces run-off & the loss of plant nutrients and carbon from soil.

How is primary rainforest in tribal lands being protected? (3 points)

• In Rondônia, the indigenous Surui people participate in a scheme that aims to protect primary rainforest on tribal lands from further illegal logging, and reforest areas degraded by deforestation in the past 40 years.

• Surui plan seedlings bred in local nurseries in deforested areas around their villages.

• The native species planted are chosen to provide them with timber for construction, food crops & through logging, a sustainable source of income.

What scheme did the Surui join in 2009? (3 points)

• 2009: Surui were the first indigenous group in Amazonia to join the UN’s Reducing Emissions from Deforestation & Degradation (REDD) scheme.

• This scheme provides payment to the tribe for protecting the rainforest & abandoning logging – market-based approach involving granting of carbon credits to the Surui.

• These credits can be purchased by international companies that have exceeded their annual carbon emissions quotas.

What did Natura do in 2013?

2013: Natura (a large cosmetics TNC) purchased 120,00 tonnes of carbon credits from the Surui – this was the first carbon credit sal by indigenous people in Amazonia.

Why are new/improved agricultural techniques being introduced? (4 points)

• Farming = main cause of deforestation in Amazonia.

• However, low fertility of soils meant that permanent cultivation proved unsustainable.

• After a few years, smallholders abandoned their plots which were then converted to low quality grassland.

• Extensive ranching enterprises could scarcely support stocking leaves of one head of cattle per hectare.

How will diversification slow rates of deforestation? (2 points)

• Soil fertility can be maintained by rotational cropping & combining livestock & arable operations.

• Integrating crops & livestock could allow a fivefold increase in ranching productivity and help slow rates of deforestation.

What are the techniques used by scientists to modify the soils for farming? (5 points)

• Natural resources for farming in the region are too poor to support settled, permanent cultivation.

• However, this is contradicted by European explorers who observed that the Amazon rainforest supported high population densities and many large urban centres as late as 16^th century.

• The explanation is though to be human-engineered soils – dark-soils made from inputs of charcoal, waster & human manure.

• Charcoal in these soils attracts micro-organisms and fungi & allows the soils to retain their fertility long-term.

• Scientists are currently investigating these dark-soils – if they can be successful recreated they would allow intensive & permanent cultivation which would drastically reduce deforestation and carbon emissions.