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Sweep Nets

August 29, 2010

Meg sweeps a teff field (teff is the cereal grain used to make the Ethiopian sour bread called injera)

The sweep net is the type of gear that I have always associated with entomologists (bug scientists). Sweep nets do not target one particular type of insect. Like beating sheets, they are used to sample for diversity and abundance. 20 half sweeps of the net samples 10 cubic meters. The nets are meant to be swept through foliage not above foliage, which is how my untrained mind would try to use it. Having one in hand gives me a strong urge to go chasing butterflies.

A happy helper of ours - I've often been asked where these children come from. Essentially, they see us drive up to the forest and curiosity does the rest.

Meg and I sampled by sweep net along the forest edge at both sites and in the barley and teff fields in Debresena. We also swept amongst Eucalyptus stands to see if we came up with a different set of insects. Without the data in front of me, I know that there were fewer insect orders and smaller numbers  of the ones that were present. As an introduced species, the eucalypts do not have many natural herbivores or inhabitants – in stark contrast to the native species. Though eucalyptus may be a good lumber and fuel crop, it doesn’t perform the same ecosystem services (home for pollinators, seed dispersers, seed germinators, herbivores, etc.) that native species do. If I haven’t mentioned it before, eucalypts are a huge drain on the water table and compete directly with local flora for water. The eucalupt fields are also difficult to recover once the trees have been harvested. The roots and stumps are difficult to remove and the soil is degraded.

Right outside the forest, amidst a Eucalypt grove, a man carries even more Eucalypt seedlings to be planted somewhere nearby

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