Do Plants Prevent Atmospheric CO2 Levels from Falling Too Far?

by Emil Morhardt

A recent paper discussed in the previous post (Galbraith and Eggleston, 2017) claims that during the past 800,000 years when the Earth has been in a glacial condition with the occasional interglacial period (such as now), there is a strong correlation between global temperature and atmospheric CO2 levels, and that they tend to go to the same low point again and again and stay there. These authors argue that if CO2 were to go lower, so would the temperature, and that therefore something is keeping the CO2 level from going any lower then 190 ppm. One intriguing possibility they bring up comes from a paper (Pagani et al., 2009) by Mark Pagani at Yale, and his colleagues at the Carnegie Institution in Stanford and at the University of Sheffield who claim that plants stop effective photosynthesis if CO2 levels fall below 190 ppm, depriving the carbon cycle of two sources of removal of atmospheric CO2; photosynthesis, and a more subtle plant activity called biologically enhanced silicate chemical weathering. The mechanisms of these two processes are interesting. Continue reading

How a Crucial Tropical Forest is Responding to Climate Change

by Pushan Hinduja

How are Mangrove forests throughout tropical areas of the world responding to the rising sea levels attributed to climate change? Daniel M. Alongi, of the Australian Institute of Marine Sciences, analyzed historic responses to changes in sea levels in Mangrove forests as well as current data to determine how well these forests are reacting to the climate crisis (Alongi 2015). Mangrove forests tend to occupy the border between land and sea in low latitudes, making them especially susceptible to the effects of climate change. Fortunately for mangroves, they have an outstanding ecological stability, in part due to their large subterranean storage capabilities. However, despite responses to develop resilience to environmental disturbances, mangrove forests are still suffering. In terms of human impact, mangrove forests are being deforested at a rate of 1-2% per year, leaving only about a century before these forests disappear entirely. Mangroves are crucial to the environment; they serve as breeding and nursery grounds for fish, birds and other animals, prevent erosion and damage from natural disasters like tsunamis, serve as a renewable source of wood for fuel, and are key components in filtering ocean contaminants. Continue reading

The Power of Green Space for Reducing Surface Temperature in Tel Aviv, Israel

by Dan McCabe

One key objective of sustainable urban planning is to limit the urban heat island (UHI) effect, the increased local temperature in highly built areas due to differences from the natural environment in the absorption and reflection of solar energy at the surface. Previous research has displayed the value of large urban parks in controlling temperature in cities, but less is known about the effect of smaller green spaces. In order to investigate how vegetation and construction levels impact UHI severity, Rotem-Mindali et al. (2015) used ten years of remotely sensed data from two NASA satellites to analyze the relationship between different land uses and land surface temperature (LST) in Tel Aviv, Israel. The authors compiled information on local LST and Normalized Difference Vegetation Index (NDVI), a measure of vegetation cover, and used it to search for a correlation between land use type and mean surface temperature for summer nights. In their analysis, they found an enormous difference of 13°C in mean temperature among different locations in Tel Aviv. There was a strong correlation between land use type and LST, with the most vegetated regions experiencing much lower average temperatures than highly built regions. Continue reading

How Many Benefits Does Commercial Forestry Provide?

by Emil Morhardt

Forestry economists worry about whether foresters can claim more societal benefits, including offsetting the effects of climate change, from forestry than merely the increased supply of trees; in econ-speak, “…what change in human well-being results from increasing, reducing or qualitatively varying…” the supply of ecosystem services commercial forests provide? Colin Price (2014) addresses this question largely in the abstract by providing an overview of eight general approaches to valuing non-market effects, which, although they break little new ground, provide an extremely clear overview of a generally murky subject. Continue reading