Context

• Recently, scientists in Canada have reported that honey can be a sensitive indicator of air quality.
• Organic things carry coded messages about their home environments, tree rings can tell scientists what the atmosphere was like when the tree was young. Similarly, lichens (unions of algae and fungi) can reveal local air pollution levels.

About

• A survey of urban beehives around Vancouver showed that the hives’ honey contained minute levels of lead.
• And with urban hives growing in number, tracking their pollutant levels may offer an inexpensive way to monitor what’s in the air all over the world.

How honey serves as a sensitive pollution detector:

• The chemistry of different samples can reveal where the honey came from.
• Volcanoes, river rocks, coal and other natural sources of lead have their own distinctive signatures, based on the ratio of different isotopes of the heavy metal in them.

Lichens can reveal local air pollution levels:

• Despite lichens' extraordinary adaptability and ability to survive in all kinds of environmental extremes, they are acutely sensitive to a major industrial atmospheric pollutant, sulphur dioxide.
• In the atmosphere, sulphur dioxide can be transformed into acid rain, which, surprisingly, does not damage lichens.
• Typically, lichens like it where the environment is moist and sunny at least some of the time, although many species of lichens can tolerate extremes of heat or cold, wetness or dryness.
• Slowly, the acids and other compounds produced and released by lichens, as well as the mechanical force of lichen growth, can disintegrate rocks and wood and turn them into soil.
• When conditions that favour growth are absent, they simply lie dormant until the condition improves.
• Approximately half the 20,000 known species of lichens produce compounds with antibiotic properties, many of which are used medicinally by native populations.

Tree-Rings and the coded messages they convey:

• A team led by scientists at the University of Arizona has attempted to connect the on-going drought to an expansion of the tropics caused by climate change.
• The study reported that the northern edge of the tropics has moved up to 4 degrees north and 4 degrees south of its standard location of 30 degrees north latitude.
• This means that the dry regions at the edge of the tropics are becoming larger.
• Changes in the Earth's climate system affect the movement of the tropics.
• The team used the annual rings of trees from five different locations across the Northern Hemisphere to track the tropical belt's movement from the year 1203 to 2003.
• Each annual growth ring of a tree reflects the climate in the tree's location that year.