Geology topics

Esther N. Githumbi

Publications and source records attributed to Esther N. Githumbi.

4 recordsLinked to original sources

USGS2026

Unprecedented burning in tropical peatlands during the 20th century compared to the previous two millennia

Tropical peatland wildfire incidence has risen in recent decades, driven by drainage for land use and intensified by severe droughts with global climate change. These disturbances have altered vegetation structure, disrupted ecosystem functioning, and increased carbon emissions, particularly in Southeast Asia. However, the long-term history and characteristics of wildfires in tropical peatlands remain largely unknown. Here, we compiled fifty-eight macro-charcoal records from peatlands across the tropics, ranging from lowland forested to montane peatlands, to assess millennia-scale changes and controlling factors of tropical peatland burning. We divided the datasets into four main sub-regions: Neotropical, Afrotropical, Indomalayan and Australasian ecoregions to explore regional variability. Tropical peatlands had high burning levels between 0 and 850 ce , followed by a relatively low and stable period until a marked increase during the 20th century. The general trend in tropical peatland burning follows changes in global temperature, and climate variables that control the length and severity of drought events have a notable influence on peat burning before 1900 ce . During the 20th century, regional differences were observed, with declining fire trends in the Neotropical and Afrotropical regions and increasing fire trends in the Indomalayan and Australasian regions. This difference is likely attributable to human activities, and such intervention is also evident in palm swamps and hardwood swamps under similar wet, weakly seasonal climates. With the increase in anthropogenic pressures on peatlands and greater climate variability, future wildfires in peatlands are likely to become more frequent and widespread across all tropical ecoregions. Conservation and sustainable land-use practices could be used to mitigate and control peatland burning and protect these carbon-rich sinks.

Global Change Biology↗

USGS2018

Latitudinal limits to the predicted increase of the peatland carbon sink with warming

The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around AD 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.

Nature Climate Change↗

USGS2018

Global Modern Charcoal Dataset (GMCD): A tool for exploring proxy-fire linkages and spatial patterns of biomass burning

Progresses in reconstructing Earth's history of biomass burning has motivated the development of a modern charcoal dataset covering the last decades through a community-based initiative called the Global Modern Charcoal Dataset (GMCD). As the frequency, intensity and spatial scale of fires are predicted to increase regionally and globally in conjunction with changing climate, anthropogenic activities and land-use patterns, there is an increasing need to further understand, calibrate and interrogate recent and past fire regimes as related to changing fire emissions and changing carbon sources and sinks. Discussions at the PAGES Global Paleofire Working Group workshop 2015, including paleoecologists, numerical modelers, statisticians, paleoclimatologists, archeologists, and anthropologists, identified an urgent need for an open, standardized, quality-controlled and globally representative dataset of modern sedimentary charcoal and other sediment-based fire proxies. This dataset fits into a gap between metrics of biomass burning indicators, current fire regimes and land cover, and carbon emissions inventories. The dataset will enable the calibration of paleofire data with other modern datasets including: data of satellite derived fire occurrence, vegetation patterns and species diversity, land cover change, and a range of sources capturing biochemical cycling. Standardized protocols are presented for collecting and analyzing sediment-based fire proxies, including charcoal, levoglucosan, black carbon, and soot. The GMCD will provide a publicly-accessible repository of modern fire sediment surface samples in all terrestrial ecosystems. Sample collection and contributions to the dataset will be solicited from lacustrine, peat, marine, glacial, or other sediments, from a wide variety of ecosystems and geographic locations .

Quaternary International↗

USGS2016

One thousand years of fires: Integrating proxy and model data

The current fires raging across Indonesia are emitting more carbon than the annual fossil fuel emissions of Germany or Japan, and the fires are still consuming vast tracts of rainforest and peatlands. The National Interagency Fire Center (www.nifc.gov) notes that 2015 is one worst fire years on record in the U.S., where more than 9 million acres burned -- equivalent to the combined size of Massachusetts and New Jersey. The U.S. and Indonesian fires have already displaced tens of thousands of people, and their impacts on ecosystems are still unclear. In the case of Indonesia, the burning peat is destroying much of the existing soil, with unknown implications for the type of vegetation regrowth. Such large fires result from a combination of fire management practices, increasing anthropogenic land use, and a changing climate. The expected increase in fire activity in the upcoming decades has led to a surge in research trying to understand their causes, the factors that may have influenced similar times of fire activity in the past, and the implications of such fire activity in the future. Multiple types of complementary data provide information on the impacts of current fires and the extent of past fires. The wide array of data encompasses different spatial and temporal resolutions (Figure 1) and includes fire proxy information such as charcoal and tree ring fire scars, observational records, satellite products, modern emissions data, fire models within global land cover and vegetation models, and sociodemographic data for modeling past human land use and ignition frequency. Any single data type is more powerful when combined with another source of information. Merging model and proxy data enables analyses of how fire activity modifies vegetation distribution, air and water quality, and proximity to cities; these analyses in turn support land management decisions relating to conservation and development.

Frontiers of Biogeography↗