Modeling land use change and forest carbon stock changes in temperate forests in the United States

Lucia A Fitts,Matthew B Russell,Grant M Domke,Joseph K Knight

doi:10.1186/s13021-021-00183-6

Abstract

BackgroundForests provide the largest terrestrial sink of carbon (C). However, these C stocks are threatened by forest land conversion. Land use change has global impacts and is a critical component when studying C fluxes, but it is not always fully considered in C accounting despite being a major contributor to emissions. An urgent need exists among decision-makers to identify the likelihood of forest conversion to other land uses and factors affecting C loss. To help address this issue, we conducted our research in California, Colorado, Georgia, New York, Texas, and Wisconsin. The objectives were to (1) model the probability of forest conversion and C stocks dynamics using USDA Forest Service Forest Inventory and Analysis (FIA) data and (2) create wall-to-wall maps showing estimates of the risk of areas to convert from forest to non-forest. We used two modeling approaches: a machine learning algorithm (random forest) and generalized mixed-effects models. Explanatory variables for the models included ecological attributes, topography, census data, forest disturbances, and forest conditions. Model predictions and Landsat spectral information were used to produce wall-to-wall probability maps of forest change using Google Earth Engine.ResultsDuring the study period (2000–2017), 3.4% of the analyzed FIA plots transitioned from forest to mixed or non-forested conditions. Results indicate that the change in land use from forests is more likely with increasing human population and housing growth rates. Furthermore, non-public forests showed a higher probability of forest change compared to public forests. Areas closer to cities and coastal areas showed a higher risk of transition to non-forests. Out of the six states analyzed, Colorado had the highest risk of conversion and the largest amount of aboveground C lost. Natural forest disturbances were not a major predictor of land use change.ConclusionsLand use change is accelerating globally, causing a large increase in C emissions. Our results will help policy-makers prioritize forest management activities and land use planning by providing a quantitative framework that can enhance forest health and productivity. This work will also inform climate change mitigation strategies by understanding the role that land use change plays in C emissions.

Highlights

Forests provide the largest terrestrial sink of carbon (C)
From 2000 until 2017, California, Colorado, New York, and Wisconsin had an increase in mean aboveground live biomass, while Georgia and Texas had a mean reduction in live biomass
Mean biomass for standing dead trees increased in California, Georgia, New York, and Wisconsin (Table 1)

Summary

Introduction

Forests provide the largest terrestrial sink of carbon (C). these C stocks are threatened by forest land conversion. As part of their ecosystem services, serve as the world’s largest terrestrial sink of carbon (C) by storing it in biomass and soil [1,2,3] This C cycles through the ecosystem via biogeochemical processes causing it to move between different pools, (i.e., aboveground and belowground biomass, dead wood, litter, organic soil, Fitts et al Carbon Balance Manage (2021) 16:20 and harvested wood products) or back to the atmosphere depending on the ecosystem’s dynamics and disturbances. When quantifying C at a large geographic scale, land use and land cover change and disturbance history are essential components to consider [3, 5, 6] In this matter, land use dynamics [2, 6,7,8], including land use legacies [7, 9], are major factors affecting terrestrial C fluxes. When quantifying C at a stand-level scale, land use change is rarely incorporated [10], creating uncertainties in C accounting

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