scholarly journals Resilience of Tropical Ecosystems to Ocean Deoxygenation

2021 ◽  
Vol 36 (3) ◽  
pp. 227-238
Author(s):  
Andrew H. Altieri ◽  
Maggie D. Johnson ◽  
Sara D. Swaminathan ◽  
Hannah R. Nelson ◽  
Keryn B. Gedan
Keyword(s):  
Tropical Ecosystems ◽  
Ocean Deoxygenation

scholarly journals Ocean deoxygenation, the global phosphorus cycle and the possibility of human-caused large-scale ocean anoxia

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160318 ◽  
Author(s):  
Andrew J. Watson ◽  
Timothy M. Lenton ◽  
Benjamin J. W. Mills
Keyword(s):  
Chemical Weathering ◽  
Large Scale ◽  
Oxygen Demand ◽  
Subsurface Water ◽  
Phosphorus Cycle ◽  
Low Oxygen ◽  
Positive Feedbacks ◽  
Future Possibility ◽  
Warming World ◽  
Ocean Deoxygenation

The major biogeochemical cycles that keep the present-day Earth habitable are linked by a network of feedbacks, which has led to a broadly stable chemical composition of the oceans and atmosphere over hundreds of millions of years. This includes the processes that control both the atmospheric and oceanic concentrations of oxygen. However, one notable exception to the generally well-behaved dynamics of this system is the propensity for episodes of ocean anoxia to occur and to persist for 10 5 –10 6 years, these ocean anoxic events (OAEs) being particularly associated with warm ‘greenhouse’ climates. A powerful mechanism responsible for past OAEs was an increase in phosphorus supply to the oceans, leading to higher ocean productivity and oxygen demand in subsurface water. This can be amplified by positive feedbacks on the nutrient content of the ocean, with low oxygen promoting further release of phosphorus from ocean sediments, leading to a potentially self-sustaining condition of deoxygenation. We use a simple model for phosphorus in the ocean to explore this feedback, and to evaluate the potential for humans to bring on global-scale anoxia by enhancing P supply to the oceans. While this is not an immediate global change concern, it is a future possibility on millennial and longer time scales, when considering both phosphate rock mining and increased chemical weathering due to climate change. Ocean deoxygenation, once begun, may be self-sustaining and eventually could result in long-lasting and unpleasant consequences for the Earth's biosphere. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

Tropical Ecosystems into the 21st Century

Science ◽  
2004 ◽  
Vol 306 (5694) ◽  
pp. 227b-228b ◽  
Author(s):  
K. S. Bawa
Keyword(s):  
21St Century ◽  
Tropical Ecosystems

Improved fuel moisture prediction in non-native tropical Megathyrsus maximus grasslands using Moderate-Resolution Imaging Spectroradiometer (MODIS)-derived vegetation indices

2017 ◽  
Vol 26 (5) ◽  
pp. 384
Author(s):  
L. M. Ellsworth ◽  
A. P. Dale ◽  
C. M. Litton ◽  
T. Miura
Keyword(s):  
Vegetation Index ◽  
Vegetation Indices ◽  
Fuel Moisture ◽  
Fire Behaviour ◽  
Native Grass ◽  
Tropical Ecosystems ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Live Fuel Moisture ◽  
Moderate Resolution Imaging Spectroradiometer

The synergistic impacts of non-native grass invasion and frequent human-derived wildfires threaten endangered species, native ecosystems and developed land throughout the tropics. Fire behaviour models assist in fire prevention and management, but current models do not accurately predict fire in tropical ecosystems. Specifically, current models poorly predict fuel moisture, a key driver of fire behaviour. To address this limitation, we developed empirical models to predict fuel moisture in non-native tropical grasslands dominated by Megathyrsus maximus in Hawaii from Terra Moderate-Resolution Imaging Spectroradiometer (MODIS)-based vegetation indices. Best-performing MODIS-based predictive models for live fuel moisture included the two-band Enhanced Vegetation Index (EVI2) and Normalized Difference Vegetation Index (NDVI). Live fuel moisture models had modest (R2=0.46) predictive relationships, and outperformed the commonly used National Fire Danger Rating System (R2=0.37) and the Keetch–Byram Drought Index (R2=0.06). Dead fuel moisture was also best predicted by a model including EVI2 and NDVI, but predictive capacity was low (R2=0.19). Site-specific models improved model fit for live fuel moisture (R2=0.61), but limited extrapolation. Better predictions of fuel moisture will improve fire management in tropical ecosystems dominated by this widespread and problematic non-native grass.

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