Wildfires can spread at shocking speeds, burn thousands of acres of land and consume everything in their path. Hawaii is not historically known for wildfires, but just like any other country in the world, it is increasingly under siege from climate extreme events. As the US is expected to get hotter and drier with climate change, the risk of wildfires is also increasing. Hawaii has been at high risk lately; this month alone, the federal government declared six different fire disasters in Hawaii! As per FEMA’s National Risk Index, the Maui County of Hawaii, which bore the brunt of the recent wildfire, has a higher risk index than nearly 88% of the counties in the US. According to the federal government’s National Climate Assessment and the National Interagency Fire Center, the average burned area due to wildfires in the US increased three-fold post-1980s. In contrast, the average burned area in Hawaii increased five-fold post-1980s, said University of Hawaii Manoa fire scientist Clay Trauernicht.
“We’ve been getting these large events for the last 20 to 30 years,” he said from Oahu.
Millions of acres of cropland have been replaced with grasslands. “These grasses can just dry out in a few weeks, and it doesn’t take extreme conditions to make them flammable”, said Stanford University climate scientist Chris Field.
The interval of June to August 2023 was a period of worsening drought in Hawaii. As the drought worsened, the fires were exacerbated by the large tracts of the dried vegetation.
As per our analysis, the wildfire that started on the night of 8th August 2023 burned through 31.31% of the land area in the four islands of Maui, Kahoolawe, Malakal and Lanai. Nearly 4,942 acres of land (about 20 square kilometres) experienced severe burning, and almost 68,942 acres (about 280 square kilometres) experienced moderate burning. As of August 15th, the officials estimated that 3,200 acres of land had burned due to wildfires.
We also analyzed the reduction in vegetation cover as a result of the recent wildfires. Using the Normalized Difference Vegetation Index (NDVI), we identified the area under vegetative cover before and after the fire. There is a reduction in sparse vegetation (crops and grass) by 12.42 acres, moderate vegetation (agroforestry) by 264.37 acres, and dense vegetation (forest) by 3,646.3 acres.
As the world warms, as the wildfires increase in number, the air pollution caused by wildfires is also expected to surge. Wildfire smoke is a mixture of hazardous air pollutants, such as CO, NO2, ozone, aromatic hydrocarbons, or lead and poses serious risks to human health. With the episodes of wildfires becoming frequent either due to climate change or anthropogenic processes, there is a need to monitor the pollutants and analyze the influence of fires on the air quality. There is a significant increase in the concentration of some pollutants during wildfires, as shown below.
We noticed a significant increase in the UV aerosol index, which is a measure of the episodic aerosol plumes from dust outbreaks. The chemicals released from the wildfire can trigger chemical reactions that erode the protective ozone layer. As shown below, we noticed a decrease in the ozone concentration in and around Maui island during the wildfire.
To summarise, we demarcated the burnt areas in the islands of MalokaI, Lanai, Kahoolwe and Maui using NBR on Sentinel-2 satellite imagery. The results show a total burnt area of 950.77 km2 , which is 31.31% of total area. We also computed the reduction in the area under vegetation using NDVI on Sentinel-2 satellite imagery. The results show that the dense vegetation which includes the forest land reduced by 3646.3 acres. In addition, the pollutants were monitored pre-wildfire and post-wildfire. There is a clear increase in the concentration of pollutants NO2, SO2, CO, and CH4. We noticed a decrease in the ozone concentration during the wildfire. There is also a significant increase in the aerosol index which measures the episodic aerosol plumes from dust outbreaks.
Wildfires will only get worse. Will wildfires start a new era of air pollution? The fires have torn through vegetation, released toxin chemicals, polluted the air and water, and affected not just humans but also the flora and fauna of the area. Experts warn that climate change-related disasters, such as the one unfolding in Hawaii, will only get more intense and more frequent.
Disclaimer: The emperical data / numbers quoted in the article to quantify the impact of the Hawaiian wildfire is based on our research analysis only and not part of any offical report.