Significance: The state of California has a globally important economy and a population exceeding 38 million. The state relies on its forested watersheds to support numerous services, such as water provisioning, carbon storage, timber products, ecotourism, and recreation. However, secular changes in air temperature, combined with periodic and prolonged drought, pose a compounding challenge to forest health. Here we use new remote-sensing and modeling techniques to assess changes in the canopy water content of California’s forests from 2011 to 2015. Our resulting maps of progressive canopy water stress identify at-risk forest landscapes and watersheds at fine resolution, and offer geographically explicit information to support innovative forest management and policies in preparation for climate change.

Carbon dioxide and methane emissions are the two primary anthropogenic climate-forcing agents and an important source of uncertainty in the global carbon budget. Uncertainties are further magnified when emissions occur at fine spatial scales (<1 km), making attribution challenging. We present the first observations from NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) imaging spectrometer showing quantification and attribution of fine-scale methane (0.3 to 73 tonnes CH ₄ hour ⁻¹ ) and carbon dioxide sources (1571 to 3511 tonnes CO ₂ hour ⁻¹ ) spanning the oil and gas, waste, and energy sectors. For selected countries observed during the first 30 days of EMIT operations, methane emissions varied at a regional scale, with the largest total emissions observed for Turkmenistan (731 ± 148 tonnes CH ₄ hour ⁻¹ ). These results highlight the contributions of current and planned point source imagers in closing global carbon budgets.

The carbon gain in restored logged forest: There is currently great interest in the capacity of global forest to store carbon and hence contribute to the mitigation of climate change in the coming decades. In a study of Southeast Asian tropical forest, Philipson et al. show that active restoration of logged forests generates higher rates of carbon accumulation than naturally regenerating forest. To estimate the economic feasibility of restoration treatments, they modeled the carbon price required to offset the cost of restoration, finding that the highest prices seen in recent years would be needed to approach those that could offset restoration costs. These results are important for tropical forest policy, establishing the importance of restoration for the carbon recovery potential of tropical forests. Science , this issue p. 838

Severe drought has the potential to cause selective mortality within a forest, thereby inducing shifts in forest species composition. The southern Sierra Nevada foothills and mountains of California have experienced extensive forest dieback due to drought stress and insect outbreak. We used high‐fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) from the Carnegie Airborne Observatory (CAO) to estimate the effect of forest dieback on species composition in response to drought stress in Sequoia National Park. Our aims were (1) to quantify site‐specific conditions that mediate tree mortality along an elevation gradient in the southern Sierra Nevada Mountains, (2) to assess where mortality events have a greater probability of occurring, and (3) to estimate which tree species have a greater likelihood of mortality along the elevation gradient. A series of statistical models were generated to classify species composition and identify tree mortality, and the influences of different environmental factors were spatially quantified and analyzed to assess where mortality events have a greater likelihood of occurring. A higher probability of mortality was observed in the lower portion of the elevation gradient, on southwest‐ and west‐facing slopes, in areas with shallow soils, on shallower slopes, and at greater distances from water. All of these factors are related to site water balance throughout the landscape. Our results also suggest that mortality is species‐specific along the elevation gradient, mainly affecting Pinus ponderosa and Pinus lambertiana at lower elevations. Selective mortality within the forest may drive long‐term shifts in community composition along the elevation gradient.