Frozen Frogs

Written by charlie   
Wednesday, 01 July 2015 19:46
In my post last month about the arrival of spring peepers and wood frogs, I brushed over a portion of their lifecycle, which deserved more attention. In the Northeast USA, both spring peepers and wood frogs go through a similar hibernation cycle during the late fall to prepare the frogs to overwinter. Adaptations to freezing is not unheard of, arctic flounder have long been known to create a protein in their blood which binds to destructive ice crystals to minimize their growth, allowing them to remain mobile and thrive in the far North seas. The gene which controls the protein, was eventually incorporated into a modified tomato increase frost tolerance, but it was never commercially available due to public outcry.

The Alaskan Wood frog take a different approach to cold weather. Rather than avoiding freezing, it is embraced, but managed in such a way that tissue and organ damage is nonexistent. The frogs increase the level of glucose in their tissue in the late fall, forcing water to remain inside the cells, inhibiting ice crystal formation.

When the temperature falls below freezing, up to 60% of the frogs body is frozen solid and its respiration and heart cease for the duration. In Alaska, the frogs are frozen for most of the winter, approximately 7 months. In more temperate areas, the frog goes through the freeze and thaw cycle multiple times throughout the winter, depending on the weather. Upon the arrival of warmer weather and longer days of early spring, the frog thaws out, and starts singing!

Further Reading:

In Alaska, wood frogs freeze for seven months, thaw and hop away

Amazing Alaskan Wood Frog Freezes Solid in Winter and Comes Alive in Spring
 
 

Converting GeoPDF to GeoTIFF

Written by charlie   
Wednesday, 24 June 2015 13:56
At times, mapping data is only available in a format that is not ideal for use within GIS. A Geospatial PDF or geoPDF is one of these formats, its a great for the end user of the map, but not for utilizing or importing the data found within the map in to a GIS system. However, there are times when you only have access to a GeoPDF and not the original source data, and must use what you have on hand. Once again, the free and Open Source Geospatial Data Abstraction Library (GDAL) comes through in a pinch, with its built in tools, gdalinfo and gdal_translate.

For a comprehensive howto, the USGS's guide Converting US Topo GeoPDF Layers to GeoTIFF is good place to start.
 

Minnesota leads Nation in wetlands conversion

Written by charlie   
Sunday, 21 June 2015 23:42
Between 2008 and 2012 Minnesota converted almost 25,000 acres of wetlands to crop land, largely as a result of higher crop prices due to the push for ethanol. The research, done by the University of Wisconsin-Madison used satellite data to identify land which had been converted.

The original article is here
 
 
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