Category Archives: Peer Reviewed Article Review

value of trees

There have been a lot of studies on the value of urban trees. Well, here’s another. This one is notable for giving a canopy target at which value is maximized (30% at the property level, 38% at the county level).

The implicit value of tree cover in the U.S.: A meta-analysis of hedonic property value studies

Trees in residential neighborhoods and communities provide benefits for homeowners that are capitalized into residential property values. In this paper, we collected data from hedonic property value studies and merged these data with ancillary spatial data describing forest and socio-economic characteristics surrounding each study area to conduct a meta-analysis of the impact of tree canopy cover on the value of residential properties. The meta-analysis suggests that property-level tree cover of about 30% and county-level tree cover of about 38% maximize the implicit price of tree cover in property values. Currently, tree cover in the original study areas was about 14%, on average, around or near study properties. The empirical results, therefore suggest under investment of tree cover on private property from the perspective of individual property owners and from a societal perspective. The findings also have implications for community forest programs regarding planting trees and protection of mature trees to address potential changes in tree abundance, species diversity and stand age due to development and climate change.

green space and mental health

Here’s a new study on green space and health, based on the large-scale nurses’s study. One interesting finding is that mental health explains around 30% of the total benefit.

Exposure to Greenness and Mortality in a Nationwide Prospective Cohort Study of Women

In models adjusted for mortality risk factors (age, race/ethnicity, smoking, and individual- and area-level socioeconomic status), women living in the highest quintile of cumulative average greenness (accounting for changes in residence during follow-up) in the 250m area around their home had a 12% lower rate of all-cause non-accidental mortality (95% CI 0.82, 0.94) compared to those in the lowest quintile. Results were consistent for the 1,250m area, although the relationship was slightly attenuated. These associations were strongest for respiratory and cancer mortality. Findings from a mediation analysis suggest that the association between greenness and mortality may be at least partly mediated by physical activity, particulate matter less than 2.5 micrometers, social engagement, and depression.

scenario analysis

Maybe this is not of interest to everyone, but I am always looking for new ways to analyze and communicate the results of alternatives and scenarios.

The diversity of socio-economic pathways and CO2 emissions scenarios: Insights from the investigation of a scenarios database

The new scenario framework developed by the climate change research community rests on the fundamental logic that a diversity of socio-economic pathways can lead to the same radiative forcing, and therefore that a given level of radiative forcing can have very different socio-economic impacts. We propose a methodology that implements a “scenario discovery” cluster analysis and systematically identifies diverse groups of scenarios that share common outcomes among a database of socio-economic scenarios. We demonstrate the methodology with two examples using the Shared Socio-economic Pathways framework. We find that high emissions scenarios can be associated with either high or low per capita GDP growth, and that high productivity growth and catch-up are not necessarily associated with high per capita GDP and high emissions.

infectious disease

The Royal Society says that the annual number of disease outbreaks and types of diseases causing them have both increased since 1980, although the fraction of the population affected has actually decreased. I assume this last trend has to do with population growth. I am not sure this should be comforting. If there are more outbreaks and more different types, it seems like there would be more potential for something really bad to emerge and then get out of control. But this article isn’t really about that, it’s just a presentation of the data.

Our analyses indicate that the total number of outbreaks and richness of causal diseases have each increased globally since 1980 (figure 1a). Bacteria and viruses represented 70% of the 215 diseases in our dataset and caused 88% of outbreaks over time. Sixty-five per cent of diseases in our dataset were zoonoses that collectively caused 56% of outbreaks (compared to 44% of outbreaks caused by human-specific diseases). Non-vector transmitted pathogens were more common (74% of diseases) and caused more outbreaks (87%) than vector transmitted pathogens (table 1). Salmonellosis caused the most outbreaks of any disease in the dataset (855 outbreaks reported since 1980). However, viral gastroenteritis (typically caused by norovirus) was responsible for the greatest number of recorded cases: more than 15 million globally since 1980.

It’s interesting how we tend to be less afraid of diseases that are more common and more afraid of ones that are less common, even though a given person would be more likely to suffer from a common disease. Of course, this analysis doesn’t take into account the severity of the disease and suffering caused, which should certainly be a factor in what kinds of controls and research we invest our efforts and money in.

ecosystem disservices

This paper proposes the idea of “ecosystem disservices” to address criticisms scientists have made of the ecosystem services concept.

Limitations of the Ecosystem Services versus Disservices Dichotomy

Ongoing debate over the ecosystem services (ES) concept highlights a range of contrasting views and misconceptions. Schröter et al. (2014) summarise seven recurring arguments against the ES concept, which broadly relate to ethical concerns, translation across the science—policy interface, and how the concept’s normative aims and optimistic assumptions affect ES as a scientific approach. In particular, recent criticism has focused on how the concept is unable to address ecological complexity due to the limitations of the economic stock–flow model that ES is based on (Norgaard 2010). Acknowledging ecosystem disservices (EDS) (i.e. outcomes of ecosystem functions that negatively affect human communities) has been suggested as a way to account for this ecological complexity (McCauley 2006; Lyytimäki 2015). The impact of EDS on communities (i.e. the ‘cost’ of the action) can be measured financially, or through changes in individual or social well-being. McCauley (2006) and Lyytimäki (2015) list EDS examples like pest damage to crops, or trees removing water from watersheds.

Integration of ecological-biological thresholds in conservation decision making

Here’s another attempt to link ecological and economic systems:

Integration of ecological-biological thresholds in conservation decision making

In the Anthropocene, coupled human and natural systems (CHANS) dominate and only a few natural systems remain without drastic human influence. Conservation criteria, such as many of those proposed by conservation biologists and ecologists with reference to areas of minimal human impact, are not relevant to much of the biosphere. On the other hand, conservation criteria delineated within economics are problematic with respect to their ability to arrive at operational indicators of well-being that can be applied in practice over multi-generational time spans. CHANS are subject to the process of economic development which, under current management structures, tends to afflict natural systems and transgress planetary boundaries. Hence, designing and applying conservation criteria applicable in real world systems where human and natural systems need to interact and sustainably coexist is essential. By both recognizing the criticality of satisfying basic needs as well as the great uncertainty over the needs and preferences of future generations, the current paper seeks to incorporate strict conservation criteria into economic evaluation. Specifically, these criteria require the conservation of environmental conditions such that the opportunity for intergenerational welfare optimization is maintained. In this direction, we propose the integration of ecological-biological thresholds into decision-making and use as an example the planetary boundaries approach. As such, both conservation biologists and economists must be involved in defining operational ecological-biological thresholds which can be incorporated into economic thinking and reflect the objectives of conservation, sustainability and intergenerational welfare optimization. As a result, we delineate the axioms of an operational framework of sustainability and hence set the basis for an interdisciplinary research agenda.

more on money, economic growth, and sustainability

Here’s a new study looking at economic growth, interest rates, the money supply, and ecological footprint.

Ecological monetary economics: A post-Keynesian critique

The monetary analysis of some ecological economists currently appears to be mostly articulated around the following core: a stationary economy (and a fortiori a degrowth economy) is incompatible with a system in which money is created as interest-bearing debt. To question the relevance of the debt-money/positive interest rate/output growth nexus, this paper adopts a critical stance towards the currently emerging ecological monetary economics from the standpoint of another strand of heterodox economics – the post-Keynesian approach. In its current state, ecological monetary economics is at odds with post-Keynesian economics in its analysis of the money–growth relationship. This will be shown using the theory of endogenous money and a simple Cambridgian–Kaleckian model where debt-money and a positive interest rate are compatible with a full stationary economy.

soil and carbon sequestration

This open-access article in Nature makes a surprising claim – that much better management of agricultural soil could offset a significant portion of annual carbon emissions from all sources (not just agriculture), while also being good for ecosystems and food security.

How important, in total, is this large, varied set of land-use and management practices as a GHG mitigation strategy? One of the challenges in answering this question is to distinguish between what is technically feasible and what might be achieved given economic, social and policy constraints. A comprehensive global analysis of agricultural practices combined climate-stratified modelling of emission reductions and soil C sequestration with economic and land-use change models to estimate mitigation potential as a function of varying ‘C prices’ (reflecting a social incentive to pay for mitigation). They estimated total soil GHG mitigation potential ranging from 5.3 Pg CO2(eq) yr−1 (without economic constraints) to 1.5 Pg CO2(eq) yr−1 at the lowest specified C price (US$20 per Mg of CO2(eq)). Average rates for the majority of management interventions are modest, <1 Mg CO2(eq) ha−1 yr−1. Thus, achieving large global GHG reductions requires a substantial proportion of the agricultural land base (Fig. 2). Although the economic and management constraints on biochar additions (not assessed by ref. 19) are less well known, ref. 67 estimated a global technical potential of 1–1.8 Pg CO2(eq) yr−1 (Fig. 2).

A more unconventional intervention that has been proposed is the development of crops with larger, deeper root systems, hence increasing plant C inputs and soil C sinks. Increasing root biomass and selecting for root architectures that store more C in soils has not previously been an objective for crop breeders, although most crops have sufficient genetic plasticity to alter root characteristics substantially and selection aimed at improved root adaptation to soil acidity, hypoxia and nutrient limitations could yield greater root C inputs as well as increased crop yields. Greater root C input is well recognized as a main reason for the higher soil C stocks maintained under perennial grasses compared to annual crops. Although there are no published estimates of the global C sink potential for ‘root enhancement’ of annual crop species, as a first-order estimate, a sustained increase in root C inputs might add ~1 Pg CO2(eq) yr−1 or more if applied over a large portion of global cropland area (Fig. 2).

Thus, the overall mitigation potential of existing (and potential future) soil management practices could be as high as ~8 Pg CO2(eq) yr−1. How much is achievable will depend heavily on the effectiveness of implementation strategies and socioeconomic and policy constraints.

I tried to get a quick answer on global annual emissions in Pg CO2(eq), and failed. Now I’m out of time. I’ll figure it out some other time.

launching the cosmic-ray neutron probe…


Okay this isn’t really about an evil plot to dominate the world. It’s about measuring soil moisture.

Estimating field-scale root zone soil moisture using the cosmic-ray neutron probe

Many practical hydrological, meteorological, and agricultural management problems require estimates of soil moisture with an areal footprint equivalent to field scale, integrated over the entire root zone. The cosmic-ray neutron probe is a promising instrument to provide field-scale areal coverage, but these observations are shallow and require depth-scaling in order to be considered representative of the entire root zone. A study to identify appropriate depth-scaling techniques was conducted at a grazing pasture site in central Saskatchewan, Canada over a 2-year period. Area-averaged soil moisture was assessed using a cosmic-ray neutron probe. Root zone soil moisture was measured at 21 locations within the 500 m  ×  500 m study area, using a down-hole neutron probe. The cosmic-ray neutron probe was found to provide accurate estimates of field-scale surface soil moisture, but measurements represented less than 40 % of the seasonal change in root zone storage due to its shallow measurement depth. The root zone estimation methods evaluated were: (a) the coupling of the cosmic-ray neutron probe with a time-stable neutron probe monitoring location, (b) coupling the cosmic-ray neutron probe with a representative landscape unit monitoring approach, and (c) convolution of the cosmic-ray neutron probe measurements with the exponential filter. The time stability method provided the best estimate of root zone soil moisture (RMSE  =  0.005 cm3 cm−3), followed by the exponential filter (RMSE  =  0.014 cm3 cm−3). The landscape unit approach, which required no calibration, had a negative bias but estimated the cumulative change in storage reasonably. The feasibility of applying these methods to field sites without existing instrumentation is discussed. Based upon its observed performance and its minimal data requirements, it is concluded that the exponential filter method has the most potential for estimating root zone soil moisture from cosmic-ray neutron probe data.

how aliens could be hiding in plain site

There’s always that puzzle – if conditions were such that life could arise on this planet, and the universe is so vast that there must be similar conditions out there, and given the unfathomable amounts of time for that to happen, is it really likely or even possible that this is the only place it ever happened? And if life is actually common, how could it be that we have never detected it? One answer to the puzzle would be if sophisticated life is out there, even relatively nearby, and doesn’t want to be detected by us for some reason.

Serious people at serious universities like Columbia study this, the technology side at least if not the existential questions. If aliens are hiding from us right now, here’s one way they might be doing it. Or if we thought there was somebody bad out there (one of those infinitesimal probability, infinite consequence risks that are hard to wrap your head around) and wanted to hide, here is how we could try to do it.

A Cloaking Device for Transiting Planets

The transit method is presently the most successful planet discovery and characterization tool at our disposal. Other advanced civilizations would surely be aware of this technique and appreciate that their home planet’s existence and habitability is essentially broadcast to all stars lying along their ecliptic plane. We suggest that advanced civilizations could cloak their presence, or deliberately broadcast it, through controlled laser emission. Such emission could distort the apparent shape of their transit light curves with relatively little energy, due to the collimated beam and relatively infrequent nature of transits. We estimate that humanity could cloak the Earth from Kepler-like broadband surveys using an optical monochromatic laser array emitting a peak power of ∼30 MW for ∼10 hours per year. A chromatic cloak, effective at all wavelengths, is more challenging requiring a large array of tunable lasers with a total power of ∼250 MW. Alternatively, a civilization could cloak only the atmospheric signatures associated with biological activity on their world, such as oxygen, which is achievable with a peak laser power of just ∼160 kW per transit. Finally, we suggest that the time of transit for optical SETI is analogous to the water-hole in radio SETI, providing a clear window in which observers may expect to communicate. Accordingly, we propose that a civilization may deliberately broadcast their technological capabilities by distorting their transit to an artificial shape, which serves as both a SETI beacon and a medium for data transmission. Such signatures could be readily searched in the archival data of transit surveys.