Australian businesses have bought into a carbon credit scheme that promised to regenerate Zimbabwean forest but is now under investigation for allegedly selling worthless emissions offsets.  Origin Energy, KPMG, and Zoos Victoria are among the entities that bought credits from the Kariba REDD+ Forest Project, which is being investigated by international greenhouse crediting organisation Verra.  …Australia’s official carbon assessor, Climate Active, has frozen applications from businesses wanting to use Kariba credits to offset their emissions.  …The scheme promised to reforest a vast tract of Kariba in north Zimbabwe which had been devastated by trophy hunting and subsistence farmers clearing trees to plant crops, gather firewood and graze animals.  But earlier this month, The New Yorker magazine ran a feature that alleged the Kariba credits were overvalued or worthless.