Image from TERRA
Thu, 05 Nov 2020 13:05 EST

Annapolis, Maryland; Norfolk, Virginia; and Miami were originally built and mapped to provide enough protection against flooding, but sea level rise has caused that buffer to shrink.

Image from TERRA
Thu, 22 Oct 2020 11:00 EDT

NASA scientists are combining data from water samples containing fish DNA with satellite data to find native fish and identify their habitats.

Image from TERRA
Fri, 25 Sep 2020 10:00 EDT

The August Complex Fire and others this fire season have been sending far-reaching plumes of wildfire smoke into the atmosphere that worsen air quality in California and beyond. Predicting where that smoke will travel and how bad the air will be downwind is a challenge, but Earth-observing satellites can help.

Terra Helps See Earth’s 3 Trillion Trees

global.fallA recent study published in Nature now estimates that there are 3.04 trillion trees on Earth, a number that is almost 8 times higher than previous estimates

Scientists rely primarily on remotely-sensed to obtain estimates of global tree populations. Satellites provide the best opportunity to achieve a global perspective, but their view of tree forest canopies from above tends to obscure individual trees and shorter trees, making it difficult to make accurate estimates. In addition, satellites are limited by their spatial resolution, not every tree is as obvious as a Redwood alone in a field. The Redwood example also points to another complication, the definition of a tree, which for most studies, including the one in Nature, is vegetation with woody stems 10 cm in diameter or larger at chest height. Thus, counting trees is a difficult process because they can vary in size and can hide beneath the canopy of larger trees, as well as be too small to be seen in satellite images.

To get a better estimate of the actual number of trees on Earth, researchers combined data from multiple vegetation indexes, including the Enhanced Vegetation Index (EVI) from the Moderate Imaging Spectroradiometer (MODIS) onboard Terra, with actual tree counts for over 430,000 hectares from 14 different biomes on Earth (there is an estimated 4 million hectares of forested land on Earth). Merging the ground measurements and applying them to the different areas of land cover visible through satellite images resulted in the more accurate estimate of tree population possible with surprisingly large results.


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