May 2022 science summary

Greetings,

This month I have a few science articles on freshwater, two on climate change and forest management, and one big one on biodiversity.

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BIODIVERSITY:
Hamilton et al. 2022 is the latest analysis from NatureServe on biodiversity in the U.S., and potential priorities for new protection. They looked at habitat for 2,216 imperiled species (G1 or G2 globally, or Threatened or Endangered nationally) across the U.S., including often overlooked species like plants and bugs. There are several interesting methodological advances here (relatively fine 1-km pixels, inclusion of overlooked species, using both range maps and habitat suitability models and showing how that changes results in Fig 4, etc.), but I think most readers will want to focus on implications for new protections and management of existing protected areas. Fig 2 shows the most important areas to protect. They use protection-weighted range-size rarity, which is a kind of rarity-weighted richness focusing on places with a) relatively high # of species that b) have relatively little habitat left nationally. Table 2 has a nice summary of how many species have the majority of their habitat managed by different groups (federal agencies, state & local, private), showing there is a lot of potential for management on existing public lands (since 43% of imperiled species have most of their habitat on public lands). It's worth reading the whole thing, but if short on time I recommend the NY Times article about this and especially the interactive maps of their data.


CLIMATE CHANGE / FOREST MANAGEMENT:
Littlefield and D'Amato 2022 looks at trade-offs between maximizing forest carbon and maximizing biodiversity and habitat quality. In particular, they note that many species require disturbance (like fire or tree removal), while maximizing carbon generally involves promoting uniformly dense and mature trees. They note that robust data looking at how different species respond to forest management are surprisingly scarce, but offer several case studies where as tree biomass increased, wildlife abundance and/or diversity has declined. They recommend that conservation planning consider climate adaptation, which means keeping landscape diversity, complexity, and connectivity (accepting that means some reduction in potential carbon), and that we explicitly discuss and recognize trade-offs where they exist.

Stephenson et al. 2014 is a global analysis of how carbon sequestration by 403 tree species change as they grow and age. 87% of tree species sequester more annual carbon per year as they get bigger (even when they get huge). On average a 1m diameter tree sequesters about triple the carbon as a 1/2m diameter tree (similar to the trunk cross-section ration of 4:1). The biggest trees can add ~0.55-0.72 t biomass (not C, which would be much lower) per year (Fig 3). However, they note that at the forest level, as an even-aged stand gets older the annual carbon sequestered per land area goes down (as trees die, total sequestration declines despite remaining big trees sequestering more. Ideally forest management should think about 1) impacts on carbon pools (how much harvested tree biomass will be lost to the atmosphere), 2) impacts on carbon sequestration, and 3) impacts on forest ecology (both mature / older trees, and disturbances and younger trees have important roles).


FRESHWATER:
Broadley et al. 2022 is a global assessment (although w/ ~1/4 of studies coming from the US) of how marine fishery productivity (including invertebrates) depends on rivers. Their headline finding is that 72% of 276 fished species (77% of global catch by mass) are linked to river flows at some point in their life cycle, and 83% eat food linked to river flows. The biggest link is occasionally going to estuaries to eat (77% of species) as opposed to diadromous or estuarine-dependent species (23% of species), see Fig 5 for a map of where they're distributed. They also offer a conceptual review of how rivers influence fisheries by focusing on science literature for the top 10 fishery species by catch mass. They conclude that rivers influence fisheries via physical changes (flow quantity, timing, and quality [sediment, nutrients, salinity, temperature, etc.]), biological response of marine species to those physical changes (e.g. nutrients from a river increasing algae which zooplankton and fish respond to, changes in spawning in response to freshwater mixing, migration, etc.), and changes in fisher behavior and fishery productivity resulting from those biological changes (see Table 1). They recommend an integrated planning approach to rivers (including dam management) and marine fisheries.

Pennock et al. 2022 makes a case that rivers with relatively natural flow regimes should be priorities for conservation (specifically protection that limits consumptive water use or otherwise alters flow). They look at four tributaties of the Green River (which feeds the Colorado River): the White, Price, San Rafael, and Duchesne Rivers. Only the White River has a relatively natural flow regime (although median spring discharge is still down 25% relative to before 1949, and summer baseflow by 29%), and spring flow in the Duchesne and San Rafel are down ~80%. That drop in flow accompanies habitat degraded in several ways: less large woody debris, narrower channels, less regeneration of cottonwoods, loss of native fish spp, etc. They also point out that even dams managed for environmental flow has fallen well short of natural flood regimes.

Maasri et al. 2022 is a new global freshwater research agenda. They have 15 recommendations in 5 themes: 1) Data infrastructure (compile and integrate data sources on freshwater biodiversity, mobilize and share existing data w/ stakeholders, and develop accessible databases), 2) Monitoring (coordinate existing FW biodiversity monitoring and move towards global consistency, expand monitoring to places and species currently overlooked [like fungi and protists], and develop new monitoring methods [like eDNA, remote sensing, citizen science, etc.]), 3) Ecology (better understand how biodiversity relates to ecosystem health and services, study how biodiversity responds to multiple stressors, and study species and ecosystem responses to global change), 4) Management (rigorous assess how well restoration works, develop management strategies aligned with "Nature Futures" scenarios based on positive human-nature relationships, and develop watershed-based integrated management and restoration programs including dam building and operation), and 5 Social ecology (co-produce solutions to conflicts between conservation and people who use freshwater systems, develop adaptive management strategies that address trade-offs with a broad coalition of participants, and promote citizen science and participatory research). I was surprised that they left off legal research into how policy mechanisms for water management are working (or not), and am somewhat skeptical that agendas like this get used, but it's a nice overview of some needs and gaps.


REFERENCES:

Broadley, A., Stewart-Koster, B., Burford, M. A., & Brown, C. J. (2022). A global review of the critical link between river flows and productivity in marine fisheries. Reviews in Fish Biology and Fisheries, 0123456789. https://doi.org/10.1007/s11160-022-09711-0

Hamilton, H., Smyth, R. L., Young, B. E., Howard, T. G., Tracey, C., Breyer, S., Cameron, D. R., Chazal, A., Conley, A. K., Frye, C., & Schloss, C. (2022). Increasing taxonomic diversity and spatial resolution clarifies opportunities for protecting US imperiled species. Ecological Applications, 32(3), 1–19. https://doi.org/10.1002/eap.2534

Littlefield, C. E., & D’Amato, A. W. (2022). Identifying trade‐offs and opportunities for forest carbon and wildlife using a climate change adaptation lens. Conservation Science and Practice, 4(4), 1–14. https://doi.org/10.1111/csp2.12631

Maasri, A., Jähnig, S. C., Adamescu, M. C., Adrian, R., Baigun, C., Baird, D. J., Batista‐Morales, A., Bonada, N., Brown, L. E., Cai, Q., Campos‐Silva, J. V., Clausnitzer, V., Contreras‐MacBeath, T., Cooke, S. J., Datry, T., Delacámara, G., De Meester, L., Dijkstra, K. B., Do, V. T., … Worischka, S. (2022). A global agenda for advancing freshwater biodiversity research. Ecology Letters, 25(2), 255–263. https://doi.org/10.1111/ele.13931

Pennock, C. A., Budy, P., Macfarlane, W. W., Breen, M. J., Jimenez, J., & Schmidt, J. C. (2022). Native Fish Need A Natural Flow Regime. Fisheries, 47(3), 118–123. https://doi.org/10.1002/fsh.10703

Stephenson, N. L., Das, A. J., Condit, R., Russo, S. E., Baker, P. J., Beckman, N. G., Coomes, D. A., Lines, E. R., Morris, W. K., Rüger, N., Álvarez, E., Blundo, C., Bunyavejchewin, S., Chuyong, G., Davies, S. J., Duque, Á., Ewango, C. N., Flores, O., Franklin, J. F., … Zavala, M. A. (2014). Rate of tree carbon accumulation increases continuously with tree size. Nature, 507(7490), 90–93. https://doi.org/10.1038/nature12914


Sincerely,
 
Jon