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Archive for Vegetation Index

Vegetation Index of Western USA

43.8N 120.5W

April 24th, 2013 Category: Climate Change, Vegetation Index

USA – April 24th, 2013

This image shows the vegetation index of western USA and southwestern Canada. Green indicates a high index, while yellow and orange indicate a low index. Some model simulations of future vegetation changes in states such as Oregon indicate that high elevation areas of subalpine forest and alpine tundra as well as areas of shrubland will contract under projected future climate changes.

These projected vegetation changes would reduce critical habitat for many species. As species distributions change, the current associations of plant species may also be affected. Some model simulations indicate that the species composition of forests may already be changing and that the rate of change will increase during the 21st-century (click here for more information).

Vegetation Index of Virginia and North Carolina, USA

36.4N 76.9W

April 4th, 2013 Category: Vegetation Index

USA – April 2nd, 2013

This image focuses on the states of Virginia and North Carolina, USA, showing the vegetation index in early Spring. The present-day climate of Virginia is generally classified as humid subtropical, but within-state variation of temperatures, precipitation, and length of growing season is dramatic. Much of the temperature gradient is related to elevation and distance from the coast, with oceanic influences greatly moderating the climate of near-coastal areas.

The relatively warm climate of eastern and southeastern Virginia is closely correlated with a concentration of southern plant species, some of which reach their northern range limits in the state. It is important to note that the contemporary vegetation of Virginia is not static and has developed only recently on the geological time scale. Ongoing global climate change and the contemporary loss of barriers to the worldwide migration of plants and other organisms will do doubt continue to generate shifts in vegetation distribution and composition across the state (click here for more information).

Vegetation Index and Climate Change in Florida, USA

27.9N 82W

April 3rd, 2013 Category: Climate Change, Vegetation Index

USA – April 2nd, 2013

This image shows the vegetation index of the state of Florida, USA (low index appears brown to yellow, while a high index appears green to dark green). Florida has abundant and unique biological resources that are expected to be negatively affected by global climate change. The state is at particularly high risk for climate change impacts because of its low topography, extensive coastline, and frequency of large storm events.

Climate change is already making large sweeping changes to Florida’s landscape, especially along the coasts. The drivers of this change are both physical and biological in nature. Changes in air and water temperature, freshwater availability, salt water intrusion, ocean acidification, natural disturbance regime shifts (e.g., fire, storms, flood), and loss of land area have already been observed in Florida. Florida’s average air temperature has increased at a rate of 0.2 – 0.40C per century over the past 160 years and is expected to increase around another 50C by 2100.

Rainfall in Florida has generally increased by 10% over the last 120 years, and more frequent heavy precipitation events are expected in the future. Both globally and in Florida, ocean pH has been lowered 0.1 unit since the pre-industrial period and another 0.3–0.5 pH unit drop is predicted by 2100. Many of Florida’s disturbances regimes such as algae blooms, wildfires, hypoxia, storms, droughts and floods, diseases, pest outbreaks are already showing signs of change. Finally, Florida’s sea level is currently rising at 1.8-2.4 mm per year and may rise by another meter by 2100.

Florida’s biodiversity is already responding to climate change through changes in physiology, distribution, phenology, and extinction risk. Physiological stress is being observed among marine species in reduced rates of calcification, photosynthesis, nitrogen fixation, and reproduction brought on by increased acidity. Northward movement is becoming more common as a result of temperature shifts. Unfortunately, for Florida, species movement brings increased risk for invasions by non-native species, like the Cuban treefrog. Sea turtle nesting and tree flowering dates are starting to shift earlier in time to keep pace with increasing temperatures in Florida. Climate change also brings elevated extinction risks for Florida’s numerous endemic species and species of conservation concern (click here for more information).

Vegetation Index of Amazon Rainforest, Brazil

4.2S 66.7W

March 27th, 2013 Category: Climate Change, Vegetation Index

Brazil – March 26th, 2013

This image shows the Normalized Difference Vegetation Index (NDVI) of the Amazon Rainforest, mostly in the Brazilian state of Amazonas. Dark green areas indicate a high index, while yellow and brown areas indicate a low index. Scientists have reported that climate change is leading to substitution of rainforest with savanna-like and semiarid vegetation, a phenomenon known as the Amazon forests’ “dieback”, particularly around the edges of the forest. Monitoring the NDVI in images such as this one allows researchers to see how fast and how much rainforest is being replaced with drier vegetation.

Comparative Vegetation Index East and West of the Andes

26.6S 68.9W

March 21st, 2013 Category: Vegetation Index

Argentina – March 21st, 2013

The Normalized Difference Vegetation Index (NDVI) is a simple graphical indicator that can be used to analyze satellite data, and assess whether the target being observed contains live green vegetation or not.

Live green plants absorb solar radiation in the photosynthetically active radiation (PAR) spectral region, which they use as a source of energy in the process of photosynthesis. Leaf cells have also evolved to scatter (i.e., reflect and transmit) solar radiation in the near-infrared spectral region. Hence, live green plants appear relatively dark in the PAR and relatively bright in the near-infrared.

The pigment in plant leaves, chlorophyll, strongly absorbs visible light (from 0.4 to 0.7 µm) for use in photosynthesis. The cell structure of the leaves, on the other hand, strongly reflects near-infrared light (from 0.7 to 1.1 µm). The more leaves a plant has, the more these wavelengths of light are affected, respectively.

Since early instruments of Earth Observation acquired data in visible and near-infrared, it was natural to exploit the strong differences in plant reflectance to determine their spatial distribution in these satellite images. Here, the color contrast shows a stark difference in the vegetation index between arid Chile and western Bolivia, which appear brown to yellow (low vegetation index), and more fertile Argentina, which appears green (high vegetation index).