Final answer:
The analogy used in 'Chasing Coral' for coral loss in the GBR in 2016 is losing most trees between Washington D.C. and Maine, highlighting the enormity of the environmental impact. The decline is attributed to coral bleaching from temperature increases and exacerbated by human activities.
Step-by-step explanation:
In the documentary Chasing Coral, an analogy is used to describe the devastating loss of coral in the Great Barrier Reef (GBR) in 2016: d. losing most trees between Washington D.C. and Maine. This imagery conveys the massive scale and impact of coral mortality, which is not immediately apparent to those without direct experience with marine environments. A loss of this magnitude is compared to the deforestation of a vast and familiar terrestrial area to help viewers comprehend the gravity of the situation.
The damage to corals is multi-faceted, resulting from factors such as climate change-induced temperature rises, which lead to coral bleaching, and human activities that increase sediment and chemical runoff in coastal areas. Increasing temperatures cause corals to expel their symbiotic algae, leading to a loss of color and vitality, a process known as bleaching. This, coupled with human-induced stressors like overfishing that disrupt the balance of marine ecosystems, has resulted in a decline of coral reefs, which are essential to marine biodiversity and provide protection for coastal regions.