A third of remaining Amazon rainforest ‘already degraded’

Sometimes, you can’t see the trees for the wood. In concentrating on the trees removed from the Amazon and the resulting loss of forest area, a study claims we have missed the devastation caused to the trees that remain.

More than a third of the world’s largest rainforest has been degraded by human activity while still classed as forest, according to the journal Science.

Whether due to drought linked to climate change, selective logging in the forest itself, or the effect of being on the edge of human habitation, the region experiences significant biodiversity loss and releases carbon into the atmosphere.

Jos Barlow, professor of conservation science at Lancaster University, said that this effect should be viewed as a problem on a comparable scale to deforestation itself.

He said: ‘‘If you’ve never been to a rainforest, you could walk in a degraded rainforest and not quite understand the difference. But if you go from an intact forest to a degraded one, then you immediately feel the difference.’’

He added: ‘‘You feel it in the heat. The understorey is three or four degrees warmer, maybe more. You feel it in the fact that it’s dry. If you walk around in a rainforest it doesn’t make any noise, but in the disturbed forest suddenly the leaves crunch under your feet. You can see it visually because it’s much lighter. You can see gaps in the canopy. You can see the sun coming in, and you can hear it as well because the sounds are different.’’

Some of the effects are consequences of the local environment and human behaviour. These include ‘‘edge effects’’, in which forests bordering human habitation end up with fewer animals and poorer quality vegetation, with fires spreading for land clearance or with larger trees being taken from within the canopy by loggers.

Barlow said that there is a chance to combat these factors, and that it might be possible to work with local populations – who can experience first-hand some of the negative effects of degraded forests, such as a rise in vector-borne diseases. Much of the degradation, however, will be harder to combat - coming as a consequence of global climate change. Some scientists fear that in the dying forest we are already seeing signs of a feared ‘‘tipping point’’ in which large swathes of the rainforest are unable to cope with the effects of rising temperatures.

‘‘It’s depressing,’’ Barlow said, ‘‘but we must have hope because this is just so important. We can’t lose it.’’