Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

In degraded landscapes, recolonization by pioneer vegetation is often halted by the presence of persistent environmental stress. When natural expansion does occur, it is commonly due to the momentary alleviation of a key environmental variable previously limiting new growth. Thus, studying the circumstances in which expansion occurs can inspire new restoration techniques, wherein vegetation establishment is provoked by emulating natural events through artificial means. Using the salt-marsh pioneer zone on tidal flats as a biogeomorphic model system, we explore how locally raised sediment bed forms, which are the result of natural (bio)geomorphic processes, enhance seedling establishment in an observational study. We then conduct a manipulative experiment designed to emulate these facilitative conditions in order to enable establishment on an uncolonized tidal flat. Here, we attempt to generate raised growth-promoting sediment bed forms using porous artificial structures. Flume experiments demonstrate how these structures produce a sheltered hydrodynamic environment in which suspended sediment and seeds preferentially settle. The application of these structures in the field led to the formation of stable, raised sediment platforms and the spontaneous recruitment of salt-marsh pioneers in the following growing season. These recruits were composed primarily of the annual pioneering Salicornia genus, with densities of up to 140 individuals/m2 within the structures, a 60-fold increase over ambient densities. Lower abundances of five other perennial species were found within structures that did not appear elsewhere in the pioneer zone. Furthermore, recruits grew to be on average three times greater in mass inside of the structures than in the neighboring ambient environment. The success of this restoration design may be attributed to the combination of three factors: (1) enhanced seed retention, (2) suppressed mortality, and (3) accelerated growth rates on the elevated surfaces generated by the artificial structures. We argue that restoration approaches similar to the one shown here, wherein the conditions for natural establishment are actively mimicked to promote vegetation development, may serve as promising tools in many biogeomorphic ecosystems, ranging from coastal to arid ecosystems

Future response of global coastal wetlands to sea-level rise.

The response of coastal wetlands to sea-level rise during the twenty-first century remains uncertain. Global-scale projections suggest that between 20 and 90 per cent (for low and high sea-level rise scenarios, respectively) of the present-day coastal wetland area will be lost, which will in turn result in the loss of biodiversity and highly valued ecosystem services1-3. These projections do not necessarily take into account all essential geomorphological4-7 and socio-economic system feedbacks8. Here we present an integrated global modelling approach that considers both the ability of coastal wetlands to build up vertically by sediment accretion, and the accommodation space, namely, the vertical and lateral space available for fine sediments to accumulate and be colonized by wetland vegetation. We use this approach to assess global-scale changes in coastal wetland area in response to global sea-level rise and anthropogenic coastal occupation during the twenty-first century. On the basis of our simulations, we find that, globally, rather than losses, wetland gains of up to 60 per cent of the current area are possible, if more than 37 per cent (our upper estimate for current accommodation space) of coastal wetlands have sufficient accommodation space, and sediment supply remains at present levels. In contrast to previous studies1-3, we project that until 2100, the loss of global coastal wetland area will range between 0 and 30 per cent, assuming no further accommodation space in addition to current levels. Our simulations suggest that the resilience of global wetlands is primarily driven by the availability of accommodation space, which is strongly influenced by the building of anthropogenic infrastructure in the coastal zone and such infrastructure is expected to change over the twenty-first century. Rather than being an inevitable consequence of global sea-level rise, our findings indicate that large-scale loss of coastal wetlands might be avoidable, if sufficient additional accommodation space can be created through careful nature-based adaptation solutions to coastal management.Personal research fellowship of Mark Schuerch (Project Number 272052902) and by the Cambridge Coastal Research Unit (Visiting Scholar Programme). Furthermore, this work has partly been supported by the EU research project RISES-AM- (FP7-ENV-693396)

Fluxes of water, sediments, and biogeochemical compounds in salt marshes

Tidal oscillations systematically flood salt marshes, transporting water, sediments, organic matter, and biogeochemical elements such as silica. Here we present a review of recent studies on these fluxes and their effects on both ecosystem functioning and morphological evolution of salt marshes. We reexamine a simplified model for the computation of water fluxes in salt marshes that captures the asymmetry in discharge between flood and ebb. We discuss the role of storm conditions on sediment fluxes both in tidal channels and on the marsh platform. We present recent methods and field instruments for the measurement of fluxes of organic matter. These methods will provide long-term data sets with fine temporal resolution that will help scientists to close the carbon budget in salt marshes. Finally, the main processes controlling fluxes of biogenic and dissolved silica in salt marshes are explained, with particular emphasis on the uptake by marsh macrophytes and diatoms

Option Values and Penalty Fees in Concession Contracts: a Real Option Approach

Concession contracts are agreements grantingthe right to construct public works, operate and provide aservice or a good.Although most contracts include penalties for delays,evidence from ongoing concession contracts shows that timeoverruns are widespread. Uncertainty over future payoffsgenerates investment timing flexibility that, if optimallyexercised, can increase the contract value for the contractorfirm. Therefore concessionaires may find it optimal to delayirreversible investments regardless the presence of penaltyclauses. This investment timing flexibility should be takeninto account when determining the penalty fees. Followingthe Real Option Approach we model the concessionaire’soptimal investment strategy and determine the optimalpenalty fee that induces the concessionaire to comply withcontract provisions on time. The higher the concessionaire’soption value to delay, the higher the optimal penalty to beset

Time Overruns as Opportunistic Behavior in Public Procurement

This paper considers the supplier’s strategic delivery lead time in a public procurement setting as the result of the firm’s opportunistic behaviour on the optimal investment timing. In the presence of uncertainty on construction costs, we model the supplier’s option to defer the contract’s execution as a Put Option. We include in the model both the discretion of the court of law in enforcing contractual clauses (i.e. a penalty for delays) and the "quality" of the judicial system. Then, we calibrate the model using parameters that mimic the Italian procurement for public works and calculate the maximum amount that a firm is "willing to pay" (per day) to postpone the delivery date and infringe the contract provisions. Our results show that the incentive to delay is greater the higher the construction costs and their volatility, and the weaker the penalty enforcement by the courts of law

Do Policy Incentives to Buildings Energy Retrofit Encourage Homeowners\u2019 Free-Rider Behavior?

To encourage homeowners in undertaking buildings energy-efficient renovations, Governments have introduced a wide range of incentive measures. Nonetheless, the cost-effectiveness of this incentive policy is controversial. The general perception is that incentives are costly and, if they are not optimally designed, they can attract free riders and generate undesirable outcomes to efficient resource allocation and to Society. In this paper, we investigate whether investments in buildings energy retrofit (BER) are be profitable in the phasing out of incentives and if current incentive policy encourage homeowners\u2019 free-rider behavior. In detail, we analyze the investment decision of a homeowner, who has to undertake retrofit interventions of an existing building, regardless incentives are cancelled out. In detail, we develop and implement a Real Option Model to determine the investment value and its optimal timing, by modeling the opportunity to invest as a call option. Our results show that negative NPV investments may turn to be profitable if the option to defer is optimally exercised. The value of flexibility to invest adds to the investment value and make incentive schemes not necessary in encouraging investments in BER. By contrast, current fiscal incentive policy in Italy may attract free riders and generate an over-investment effect, which in turn increase costs for Government and Societ

It Is Never too Late: Optimal Penalty for Investment Delay in Italian Public Procurement Contracts

We provide a general framework in which to determine the optimal penalty fee inducing the contractor to respect the contracted delivery date in public procurement contracts (PPCs). We do this by developing a real option model that enables us to investigate the contractor’s value of investment timing flexibility which the penalty rule - de facto - introduces. We then apply this setting in order to evaluate the range of penalty fees in the Italian legislation on PPCs. According to our calibration analysis, there is no evidence that the substantial delays recorded in the execution times of Italian PPCs are due to incorrectly set penalty fees. This result opens the way for other explanations of delays in Italian PPCs: specifically, we extend our model to investigate the probability of enforcing a penalty which we assume negatively affected by the "quality" of the judicial system and the discretionality of the court in voiding the rule. Our simulations show that the penalty fee is highly sensitive to the "quality" of the judicial system. Specifically referring to the Italian case, we show that the optimal penalty should be higher than those set according to the present Italian law

A model for defining sponsorship fees in public-private bargaining for the rehabilitation of historical-architectural heritage

This paper proposes a model of support for public administrations aimed at determining the rates for the exploitation of image rights by those companies that intend to sponsor rehabilitation or restoration projects in order to en-hance the historical and architectural heritage present in Italy. This model has been applied to the city of Salerno (Italy). Indeed, it was as-sumed that the municipal administration is looking for sponsors intent on fi-nancing the restoration works of four city monuments. Through the model it was possible to determine the amount of funding, to be paid by the sponsors, including the amounts necessary for restoration works and advertising costs. The advertising fees for the city of Salerno have been determined starting from those established by Naples Municipal and applied to similar cases of cultural sponsorship. The parameter used for the comparison is the average monthly number of attendances that characterizes each location (direct audi-ence). The costs of restoration work, for each monument of Salerno, have been de-termined through expeditious bills of quantities. Finally, the total cost of sponsorship is equal to the sum of the restoration works costs and advertising costs

A Literature Review on Construction Costs Estimation: Hot Topics and Emerging Trends

The aim of the present paper is to investigate the literature on the issues of construction costs in building production and urban development in order to identify the most relevant trends and describe the research context. In particular, a bibliometric analysis was carried out through one of the most acknowledged bibliometric databases, Scopus. Due to the great number of documents related to this topic, the literature review was conducted at three different levels: the first one investigates in a wider manner the cost value, the second one analyses the costs in building production and infrastructure, whereas the third one focuses on the evaluation approaches and new trends emerging from the literature. This study has allowed an advance in the comprehension of the main relevant issues related to this topic and an in-depth understanding of the role of evaluation methods as an instrument to synthesize the full range of aspects involved in the cost and in the project life-cycle. The increasing importance of topics like Building Information Modeling (BIM), Life Cycle Assessment (LCA) or Multicriteria analysis shows clearly a transition of the research to a sustainable view of the production operations and to a life cycle perspective of the projects

Energy Audit and Multi-criteria Decision Analysis to Identify Sustainable Strategies in the University Campuses: Application to Politecnico di Torino

Universities play a headship role among entities that invest in technological progress and intend to increase education in sustainable culture towards a post-carbon society. With this in mind, Politecnico di Torino is a leader on the national and international scene. It has prepared sustainability lines for the next few years to translate the Sustainable Development Goals into concrete actions. The goal of this work is the evaluation of eight alternative energy efficiency scenarios resulting from the combination of different strategies for the retro!t of the University Campus of Politecnico di Torino. In the first part of the study, the alternatives are assessed in terms of energy performance. Subsequently, an economic evaluation supported by the multi-criteria TOPSIS method makes it possible to order the alternatives according to the opinion of several experts. The integrated evaluation allows considering a set of co-benefits generated by the project going behind the energy aspects. The best strategy involves covering electricity needs with renewable energy sources, adopting students’ engagement policies and optimizing the set-point temperature. The results highlight how low-cost solutions such as awareness campaigns and variation of the set-point temperature can bring signi!cant co-benefits from energy, economic, environmental and social perspectives