Nitrogen (N) availability relative to plant demand has been declining in recent years in terrestrial ecosystems throughout the world, a phenomenon known as N oligotrophication. The temperate forests of the northeastern U.S. have experienced a particularly steep decline in bioavailable N, which is expected to be exacerbated by climate change. This region has also experienced rapid urban expansion in recent decades that leads to forest fragmentation, and it is unknown whether and how these changes affect N availability and uptake by forest trees. Many studies have examined the impact of either urbanization or forest fragmentation on nitrogen (N) cycling, but none to our knowledge have focused on the combined effects of these co‐occurring environmental changes. We examined the effects of urbanization and fragmentation on oak‐dominated (Quercus spp.) forests along an urban to rural gradient from Boston to central Massachusetts (MA). At eight study sites along the urbanization gradient, plant and soil measurements were made along a 90 m transect from a developed edge to an intact forest interior. Rates of net ammonification, net mineralization, and foliar N concentrations were significantly higher in urban than rural sites, while net nitrification and foliar C:N were not different between urban and rural forests. At urban sites, foliar N and net ammonification and mineralization were higher at forest interiors compared to edges, while net nitrification and foliar C:N were higher at rural forest edges than interiors. These results indicate that urban forests in the northeastern U.S. have greater soil N availability and N uptake by trees compared to rural forests, counteracting the trend for widespread N oligotrophication in temperate forests around the globe. Such increases in available N are diminished at forest edges, however, demonstrating that forest fragmentation has the opposite effect of urbanization on coupled N availability and demand by trees.

After decades of pressure from vulnerable developing countries, the Warsaw International Mechanism on Loss and Damage (the WIM) was established at the nineteenth Conference of the Parties (COP 19) in 2013 to address costly damages from climate change. However, little progress has been made towards establishing a mechanism to fund loss and damage. The WIM's Executive Committee issued its first two-year workplan the following year at COP 20 which offered, among other things, a range of approaches to financing loss and damage programmes, which we review here. We provide brief overviews of each mechanism proposed by the WIM ExCom, describe their current applications, their statuses under the UNFCCC, some of their advantages and disadvantages, and their current or potential application to loss and damage. We find that several of these mechanisms may be useful in supporting loss and damage programmes, but identify three major gaps. First, most of the mechanisms identified by the WIM ExCom are insurance schemes subsidized with voluntary contributions, which may not be adequate or reliable over time. Second, none were devised to apply to slow-onset events, or to non-economic losses and damages. That is, if harms are to parts of a society or its ecosystems that have no price, or if they occur gradually, they would probably not be covered by these mechanisms. Finally, the lack of a dedicated and adequate flow of finance to address the real loss and damage being experienced by vulnerable nations will require the use of innovative financial tools beyond those mentioned in the WIM ExCom workplan. Key policy insights• Despite a full article of the 2015 Paris Agreement devoted to loss and damage, there is little international agreement on the scope of loss and damage programmes, and especially how they would be funded and by whom. • Most of the loss and damage funding mechanisms identified by the WIM ExCom are insurance schemes subsidized with voluntary contributions, which may burden the most vulnerable countries and may not be reliable over time. • None of the mechanisms were devised to apply to slow-onset events, or to non-economic losses and damages.Policy Relevance Statement: After years of arguments by developing countries for recognition of loss and damage (beyond their ability to adapt to climate impacts), a full article of the 2015 Paris Agreement was devoted to the issue. International mechanisms to address loss and damage are receiving increased attention, particularly given the intensification of climate impacts occurring and projected to occur in the coming years, and the inability of mitigation and adaptation projects to adequately address those impacts. However, there is little international agreement on the scope of loss and damage programs, and especially how they would be funded and by whom. As such, it is crucial to identify potential funding sources and assess their efficacy, reliability, and equity, so that loss and damage response programs can be institutionalized, implemented, evaluated and improved.

Silicon (Si) exports from terrestrial to marine systems can dictate phytoplankton species composition in Arctic coastal waters. Diatoms are often the dominant autotroph in Arctic waters, making Si an important control on Arctic marine primary productivity. Yet even as Arctic regions are among the fastest warming on Earth, we lack baseline knowledge on the magnitudes and controls of Arctic river Si exports. To address uncertainties in current and future Si behavior, we used a combination of field data and modeling to quantify daily yields of dissolved Si (DSi) and biogenic Si (BSi) from a 400 km space‐for‐time latitudinal gradient of seven basins across the boreal‐Arctic transition in Alaska (United States) over the course of 2 years (2015–2016). Mean annual DSi concentrations (33–149 μM) and yields (13–49 kmol km−2 year−1) were significantly and positively correlated with mean basin active layer depth, indicating that permafrost thaw will likely increase DSi fluxes to Arctic coastal waters. Conversely, BSi concentrations (7–16 μM) and yields (2.6–4.5 kmol km−2 year−1) were more uniform across the seven basins, indicating that warming may not substantially alter BSi loads to coastal systems in the near future. Our data also indicate that climatic warming will advance the timing of Si delivery to coastal waters in the spring, although the ratios of Si to nitrogen in Arctic river exports will likely remain steady. These results highlight the important role of basin hydrology, largely driven by permafrost extent, as a key driver of Si exchange at the land‐sea interface in the Arctic.