This is the accepted version of the article: Carabassa, Vicenç; Ortiz Perpiñà, Oriol; Alcañiz, Josep M. «RESTO- QUARRY: indicators for self-evaluation of ecological restoration in open-pit mines». Ecological indicators, Vol. 102 (July 2019), p. 437-445. DOI 10.1016/j.ecolind.2019.03.001 This version is avaible at https://ddd.uab.cat/record/216988 under the terms of the license 1 Title: RESTOQUARRY: indicators for self-evaluation of ecological restoration in 2 open-pit mines 3 Authors and addresses: Vicenç Carabassa1, Oriol Ortiz1,2, Josep M. Alcañiz1,3 4 1 5 CREAF, E08193 Bellaterra (Cerdanyola del Vallès), Catalonia, Spain 2 6 Escuela Politécnica Superior, University of Zaragoza, Carretera Cuarte s/n, E-22071 7 Huesca, Spain 3 8 Universitat Autònoma de Barcelona, E08193 Bellaterra (Cerdanyola del Vallès), 9 Catalonia, Spain 10  Address correspondence to V. Carabassa, phone: 0034 93 581 3355, e-mail: 11 v.carabassa@creaf.uab.es 12 13 14 Abstract 15 16 Several methods and criteria to evaluate and assess quarry restoration are available in 17 the scientific literature, but they are very specialized and time consuming. Furthermore, 18 there is a lack of evaluation tools appropriate for technicians involved in these types of 19 activities, such as quarry engineers, restoration managers and quality control 20 supervisors in public administration. The work presented attempts to bridge the gap 21 between scientific knowledge and practical needs by proposing a simplified 22 methodology (RESTOQUARRY protocol), which enables the non-scientific public to 23 evaluate restored areas. This procedure focused on five groups of parameters for zone 24 (homogeneous portions within the whole restored area) evaluation: geotechnical risk, 25 drainage network, erosion and physical degradation, soil quality and vegetation status 26 and functionality. Moreover, three groups of parameters are proposed for area (whole 27 restoration) evaluation: landscape integration, ecological connectivity and fauna, and 28 anthropic impacts. This protocol has been tested in 55 open-pit mines located 29 throughout Catalonia (NE Iberian Peninsula), covering a wide range of Mediterranean 30 climatic conditions and geological substrates. Results indicate that the proposed 31 methodology is suitable for detecting critical parameters that can determine the success 32 of the restoration. 33 34 35 Keywords: Open-pit mines reclamation; quarry rehabilitation; ecological restoration; 36 restoration evaluation; ecological indicators 37 38 Highlights 39 40 A new multicriterial procedure for integrated self-evaluation of mine restorations 41 It includes ecological, technical and socio-cultural aspects 42 It uses 34 evaluation parameters, selected and weighted by an expert panel 43 The evaluation allows to score the whole restoration 44 The score is accompanied by an interpretation of the monitoring values 45 The evaluation allows to highlight critical factors for restoration success 46 1. Introduction 47 Ecological restoration is defined by The International Society for Ecological Restoration 48 as the process of assisting the recovery of an ecosystem that has been degraded, damaged 49 or destroyed (Clewell et al., 2004), in order to retrieve its environmental functions and 50 ecosystem services. This institution provides a list of ecosystem attributes as a guideline 51 for measuring restoration success after human-induced perturbations. However, what 52 characterizes successful restoration and how best to measure it generates debate among 53 members within the scientific community (Wortley et al., 2013; Crouzeilles et al. 2016). 54 Many methods to evaluate these attributes are available in the scientific literature and 55 most studies are focused on vegetation composition and structure, biodiversity and 56 ecological processes (Ruiz-Jaen & Aide, 2005; Wortley et al. 2013). In the present paper, 57 the concept of restoration is used in a broad sense, including rehabilitation and other 58 recovering alternatives of mined sites. 59 It is well known that advances in restoration ecology are intrinsically linked to advances 60 in the ecological understanding of the ecosystems to be restored, and the knowledge of 61 soil and vegetation properties is an appropriated way to guarantee restoration success 62 (Prach, 2003; Temperton et al. 2004; Valladares and Gianoli, 2007). Moreover, 63 geotechnical stability, runoff control, landscape integration, and ecological connectivity, 64 among others, are basic site attributes to be considered for a good quality restoration, 65 especially in mining activities. However, the choice of relevant evaluation attributes 66 depends on the type of degradation processes that previously affected the restored zones. 67 Specifically, sites affected by mining activities, such as quarries, are a paradigmatic case 68 of drastic anthropic perturbation, as almost all the components and attributes of the 69 original ecosystem have been destroyed and, therefore, must be restored. 70 Practitioners have asked researchers to provide potentially useful procedures based on 71 objective indicators (Clewel & Rieger, 1997; Beier et al. 2017). On the other hand, 72 researchers have appointed the need to improve the evaluation of restorations carried out 73 in open-pit mines (Halldórsson et al. 2012, Hagen et al. 2013; Suding 2011), although the 74 available information on the topic has increased in the last years (Wortley et al. 2013). 75 Evaluation tends to be focused on the descriptive characterization of the restored areas, 76 and restricted to a single or few checks after the restoration works (Suding 2011). 77 Nonetheless, a continuous monitoring during all the restoration process is necessary 78 (Allen et al. 2002; Pander and Geist 2013) and should be coupled to the exploitation 79 works. In any case, economic and ecological results of the restoration could be improved 80 if clearer evaluation protocols exist, which also could facilitate the transfer of valuable 81 information to other projects (Nilsson et al. 2015). 82 The present work attempts to satisfy these demands for evaluating restoration of mine 83 sites, providing a scientifically based multifactorial methodology to be incorporated in 84 the decision-making process. This will lead to regaining the restoration bonds (financial 85 guarantee) that mine companies must deposit in many countries, in order to guarantee the 86 correct restoration of the degraded land. This study aims to contribute to the generation 87 of best available techniques in this field, filling the gap that already exists in the extractive 88 activities sector with an innovative methodology that takes into account a wide range of 89 geotechnical and ecological indicators. Some authors have proposed similar procedures 90 for rangelands and mine sites (Courtney et al. 2010; Dzwonko and Loster 2007; Tongway 91 and Hindley, 2004); however, these methodologies are rather inaccessible to the non- 92 scientific public, as they assess excessively specific or technical indicators. In order to 93 avoid these limitations, RESTOQUARRY protocol, a self-evaluation procedure of open- 94 pit mines restoration, is proposed (Carabassa et al. 2010; Carabassa et al. 2015). This 95 protocol is aimed to be useful for mining engineers and managers of environmental 96 agencies, who can easily put it into practice without having to have much scientific 97 knowledge about ecological restoration. If this goal is reached, better involvement by 98 extractive companies in the restoration process would also be achieved and, therefore, the 99 quality of the restorations carried out by these industries would rise. Moreover, the 100 application of participatory methodologies such as the proposed in this work would aid 101 the cooperation and communication between public administration and extractive 102 industries, which is crucial for improving restoration and finding the most appropriate 103 solution on a case by case basis. 104 105 2. Materials and methods 106 2.1 Selection of restoration indicators 107 A preliminary proposal of quality indicators/parameters of mining restoration success was 108 subjected to a screening process by experts. This proposal has been based on the know- 109 how generated in previous research projects and carried outwith the collaboration of 110 engineers of mining industries, technicians of competent authorities, ecologists from 111 NGOs, technicians from consulting companies and scientists with broad experience in 112 mine restoration. These actors constituted an expert panel including 17 people/entities. 113 After an independent review process, the first proposal of indicators was made. This 114 proposal included specific indicators applicable to homogeneous zones within the whole 115 area (zone indicators), and a set of more generalist indicators, applicable to the whole 116 restored area (area indicators). This distinction between area and zone was made in order 117 to correctly evaluate parameters that must be measured separately at slope, habitat or 118 landscape level. 119 There are five groups of zone indicators: geotechnical risk, drainage network, 120 erosion/degradation processes, soil and vegetation (Table 1). Some vegetation indicators 121 (plant cover, woody species richness and density, or herbaceous species richness) are 122 based on the comparison to a reference site, usually located in an undisturbed zone close 123 to the mine. For geotechnical risk (area affected by landslides and fallen blocks) and 124 erosion (area affected by rill erosion) indicators, the area influenced by instability 125 processes could measured directly at the field or by photointerpretation, depending on the 126 magnitude of the process. Soil bulk density is measured by the excavation method as 127 coarse particles are often abundant in this kind of substrates. Soil sampling is performed 128 using Edelman auger or similar tool to extract the first 20 cm of topsoil. The 129 recommended sampling density is specified in the protocol (20 holes/ha). Vegetation 130 measures are obtained on 10x10 m square plots, distributed along the evaluated zones, 131 and on 10 m transects delimited by the sides of these plots (horizontal and perpendicular 132 to the slope). 133 Indicators related to the area evaluation are mainly qualitative (see Table 2). This is 134 especially true for the case of landscape integration, where the proposed indicators are 135 based mainly on the perception of the evaluator. However, the protocol gives guidance in 136 order to reduce the subjectivity of the observations, allowing the evaluator to classify 137 landscape integration according to the similarity of the restored area to the surrounding 138 natural landscape. All the methods for measuring the indicators are standardized and 139 explained in Carabassa et al. (2015), including sampling density and recommendable 140 sampling period. 141 142 2.2 Transformation of indicators to restoration quality indexes 143 In order to compare and integrate the evaluation data through a set of individual 144 indicators, the use of functional curves is proposed (Figure 1). The objective is to obtain 145 a global Restoration Quality Index (RQI) that summarizes the main factors influencing 146 the restoration, using the proximity to target methodology (Rodríguez-Loinaz et al. 2015, 147 Roces-Díaz et al. 2018). A functional curve for each parameter is proposed, according to 148 the bibliographyand the knowledge and expertise of the panel members (Cortina et al., 149 2012; Deltoro et al., 2012, Jorba et al., 2010, Carabassa et al. 2010; Moreno-de las Heras 150 et al., 2008, Alcañiz et al., 2008; Tongway and Hindley, 2004; Conesa, 2003, Forman, 151 2003). These functions transform each parameter value, measured in its own units, to its 152 respective Restoration Quality units (RQx), which are standardized, dimensionless and 153 fully comparable, where 1 represents the maximum quality for restoration and 0 the worst 154 case. 155 156 2.3 Indicators weighting 157 The expert panel was invited to weight the indicators in order of importance for the 158 evaluation of the restoration success. Indicators were weighted using a pairwise 159 comparison method through a Delphi process (Okoli and Pawlowski, 2004; Mukherjee et 160 al 2015). The result of the ranking and pairwise successive comparisons gave a weight 161 (W) for each indicator according to its importance for the whole restoration success. The 162 global restoration quality index (RQI) was calculated as the sum of all the RQx multiplied 163 by its respective W: 164 RQI = ∑𝑛𝑥=𝑚 (RQx · Wx) 165 166 2.4 Study sites 167 The RESTOQUARRY protocol was assayed in a pilot test on 55 selected open-pit mines 168 distributed along NE Iberian Peninsula (Catalonia, Spain), covering different climatic 169 conditions, geological substrates, soil types and extraction procedures (Figure 2, Table 170 3). A total of 106 restored zones were evaluated in these mines applying the proposed 171 methodology. 172 The selected restored mine-zones of the pilot test included a broad range of restoration 173 goals, landscape type and age. The main restoration goal in this selection was the 174 ecological restoration, but also there were cases of conversion to agriculture and forestry 175 plantations. The surface of the evaluated areas ranged between 0.8 and 165 ha. The trial 176 areas had been restored between 4 and 21 years before the evaluation process, which 177 allowed the comparison of old restorations with new ones. 178 179 3. Results 180 3.1 Zone evaluation 181 3.1.1. Geotechnical risks 182 Flat zones and steep slopes (30-37º) were the predominant geomorphologies in the 183 selected restorations. The slope is an important factor that determines geotechnical risks, 184 soil degradation processes, and vegetation establishment. In terms of geotechnical risk, 185 fallen blocks were observed in 60% of the banks with a slope higher than 8º. Fallen blocks 186 represented big stones or boulders (> 20 cm diameter) that had fallen down from 187 extremely steeped slopes (>45º) and/or vertical walls, representing a safety risk and 188 compromising the vegetation located on the trajectory of this fall. Landslides are also 189 related to slope, and a third of the zones with a slope higher than 8º showed this type of 190 geotechnical risk. Moreover, other geotechnical risks, such as subsidences or cracks were 191 also detected, but they affected minor surfaces and in low grade. 192 3.1.2. Erosion and physical degradation 193 Regarding soil degradation processes observed, rill erosion was the most relevant. Rill 194 erosion is a concentrated water erosion process that supposes an important soil loss and 195 that could trigger the destabilization of the entire slope. Approximately half of the areas 196 with slopes of more than 30º showed rills with a depth greater than 5 cm. Areas degraded 197 by concentrated water erosion ranged between 1,053 to 40,700 m2, which represents 4 to 198 100% of the surface of the restored zones. The calculated erosion rates ranged between 199 0.2 to 27 Mg ha-1 y-1 in the affected zones. The slope is also an important factor for sheet 200 water flow as 61% of the zones with a slope greater than 30º were degraded by sheet 201 erosion. Moreover, a quarter of the evaluated zones showed surface crusts as a 202 consequence of splash. Soil compaction and subsurface erosion impacted 20% and 9% of 203 the evaluated zones, respectively. 204 205 3.1.3. Soil quality 206 Organic matter content, electrical conductivity, available phosphorous (P), total nitrogen 207 (N) content and soil depth seemed to be the most limiting factors in the evaluated soils 208 (see Table 4). Poor organic matter contents (<0.8%) were detected in four of the analyzed 209 soils, mainly in the sandy ones. Moderate to high conductivity was detected in some of 210 the soils, but in most of the cases, this was not attributable to the mining activities. A 211 quarter of the soils evaluated showed a low available P content while 12% of the soils 212 showed high levels due to organic amendments (compost, sewage sludge, or pig slurry). 213 This trend was similar to the observed for total N content. Zones with severe slope (>30º) 214 showed an average soil depth of 0.2 m (due to the difficulty of stabilizing topsoil). 215 216 3.1.4. Vegetation status and functionality 217 The herbaceous cover was dominant in the evaluated zones with an average value of 55%, 218 while mean total plant cover (including trees and bushes) was 73%. Plant cover is an 219 important factor to prevent soil losses because erosion problems are mainly detected in 220 zones with <40% of soil surface covered by plants. Bushy invasive species, such as 221 Arundo donax, were present in 19% of the evaluated zones. However, these species were 222 not extensively distributed and were found in small patches. In 81% of the evaluated 223 zones, native bushy species were identified. Reproductively mature bushes were observed 224 in 54% of the locations, and spontaneous reproduction of these species were observed in 225 45% of the cases, mainly corresponding to Santolina chamaecyparissus and Dittrichia 226 viscosa. Regarding tree species, low canopy cover and diversity were observed as only 227 17% of the zones had more than three tree species. Pinus halepensis, which was widely 228 planted for reforestation in the Mediterranean region due to its resistance to drought and 229 soil deficiencies, was the dominant species. The mortality rate of planted trees was high 230 for native Quercus species, reaching 100% in some cases. On the other hand, some of the 231 evaluated zones were affected by grazing, which negatively strained vegetation 232 development and soil quality (erosion) in the first steps of restoration. 233 234 3.2 Area evaluation 235 3.2.1. Landscape integration 236 Regarding chromatic and morphologic integration to the surrounding landscape, the 237 majority of the evaluated restorations (93%) present good results. However, in some 238 cases, the presence of artificial morphologies (cliffs in hilly landscapes, isolated tips, or 239 repetitive and linear slope-berm morphology) and the dominance of herbaceous 240 vegetation in a site surrounded by forests make this integration difficult (figure 3), at least 241 in the first stages of restoration. 242 243 3.2.2. Ecological connectivity and fauna presence 244 The presence of steep slopes or abrupt topographic changes is common on the boundaries 245 of the quarries and could act as an ecological barrier for some animal species. Moreover, 246 in the vast majority of the restored areas, structures for attracting fauna (refuges, drinking 247 troughs or woody plants with edible fruits) are missing. Nevertheless, in most of the 248 evaluated areas diverse fauna traces (mainly wild boar and rabbit traces) were observed. 249 Burrows were observed in approximately one third of the evaluated areas, and nests were 250 only observed in one quarry. 251 252 3.2.3. Anthropic impacts 253 Approximately 1/3 of the areas were affected by anthropogenic impacts of various types. 254 The most common effects were related to dumping, mainly in quarries located near to 255 urban areas, and to the presence of abandoned infrastructures and machinery (i.e. ruins of 256 buildings, sheds, conveyor belts or old bulldozers and dumpers) from the previous mining 257 activity (Figure 4). 258 259 3.3 Indicators weight 260 As a result of the expert panel weighting process, a ranking of the indicators per group 261 was made (Table 5). Zone indicators obtained greater weight than area indicators. Among 262 the zone indicators, geotechnical risk was the most relevant since stability problems of 263 the slopes compromise the success of the restoration. The presence of broken channels in 264 the drainage network, directly related to geotechnical instabilities and erosion problems, 265 was considered the second most important indicator. Geomorphologic integration was 266 rated as the third due to its implications in geotechnical risks and soil degradation. 267 According to the criteria of the expert panel and the field observations, evaluation 268 parameters with a weight higher than 2% were considered key indicators for ecological 269 restoration success and must be taken into special consideration when analyzing the 270 results of the evaluations. 271 272 3.4 Restoration Quality Index (RQI) calculation and assessment 273 Using the results of the quality indicators per zone and area, the whole RQI was 274 calculated. Most of the restorations evaluated had a global RQI >70 since the relatively 275 high number of parameters considered t make it difficult to have low RQI values. For this 276 reason, a restoration with low values in a specific key indicator could obtain a relatively 277 high global RQI value. In order to avoid that critical situations hidden by high RQI values 278 and that could threaten the restoration, the adoption of corrective measures is 279 recommended when: 280 - RQx = 0 for any indicator 281 - RQx < 0.5 for a key indicator 282 Usually, restorations with an RQI > 85 have an RQx > 0 on all key indicators. In these 283 situations it could be considered a good result, meaning that the restoration objective has 284 been achieved. However, the adoption of corrective measures could not be excluded in 285 some cases or may be recommended in order to improve some aspects to better guarantee 286 that the ecosystem transition towards a more mature and resilient state occurs. According 287 to this, we could consider that mining companies can regain the restoration bond when 288 they have obtained an RQI > 85 and an RQx > 0 for key indicators, and have adopted the 289 recommended corrective measures. An example of the application of the 290 RESTOQUARRY protocol is shown in Table 6. In this case, an RQI of 87 was achieved, 291 but soil depth, woody species richness, chromatic and textural integration, woody plants 292 with fruits, and grazing triggered warning alerts and improvement recommendations were 293 needed. It can be seen that the use of this assessment procedure gives a detailed picture 294 of the restoration status. The general overview of this example of evaluation can be that 295 the restoration goals have been reached, although issues related to plant development 296 should to be improved. 297 298 4. Discussion 299 The RESTOQUARRY protocol is a procedure that has been designed to help the 300 evaluation of open mine restorations, using objective information obtained through 301 simplified methodologies available for a non-specialized public. The protocol aims also 302 to directly involve engineers of extractive companies in the design and monitoring 303 process of the restoration of their mines, trying to respond to some demands from 304 practitioners (Clewel & Rieger, 1997; Ockendon et al. 2018). Moreover, the 305 RESTOQUARRY protocol provides a decision-making system useful for public 306 administration bodies responsible for monitoring and evaluating mine restorations. This 307 evaluation system is a very committed process, which must guarantee the correct 308 evolution of the restorations towards the desired reference (eco)system, and which must 309 maximize the provision of ecosystem services (Comín et al., 2018). In addition, this 310 evaluation process must ensure that the return of the restoration bonds deposited by 311 extractive companies is decided on an objective and quantifiable basis, and made in the 312 correct time, not unnecessary extending the guarantee time, neither shortening it. 313 The vast majority of the indicators proposed in the protocol indirectly evaluate (proxies) 314 ecosystem services and/or ecosystem functions, allowing the quantification of some of 315 them. For example, erosion control, soil fertility, nutrient recycling or nutrient retention 316 are evaluated through soil quality, soil erosion, and vegetation indicators. Even the most 317 general indicators (area indicators), such as those related to anthropic impacts or 318 landscape integration, could be considered proxies of ecosystem services linked to non- 319 material benefits obtained through experiences (for example, cultural services). 320 The RESTOQUARRY protocol allows good quality restorations to be distinguished from 321 those that need to take corrective measures (i.e. minor revision) and those that have 322 critical failures that pose a risk to all the restoration efforts made (i.e. major revision). 323 The simplicity of the protocol is not achieved at the expense of reliability or replicability 324 since it is based on a wide literature review and the extensive knowledge of a panel of 325 experts in the related fields (ecologists, quarry engineers, administration representatives). 326 Moreover, this protocol has been tested in a wide representative sample of open-pit mines, 327 with the direct participation of the end-users. One of the essential aspects of the protocol 328 is that it does not evaluate the activities that have been carried out in the restoration, but 329 rather its effective results. After applying the RESTOQUARRY protocol, we able to 330 determine the whole restoration quality and to identify the critical features that need to be 331 improved in the extractive activities assessed. Thereby most of the restorations evaluated 332 in this work need the application of corrective measures in order to achieve the minimum 333 standard quality. The RESTOQUARRY protocol also intends to be useful at the stage of 334 restoration design, as it provides evaluation criteria that will be applied at the end of the 335 restoration works. Engaging mine workers and engineers in the evaluation of restoration 336 helps to improve the restoration works and their implication in the restoration process, 337 which consequently could enhance the quality of the restorations carried out by these 338 companies. 339 340 4.1 Similarities and differences with other evaluation procedures 341 Despite there being lots of studies evaluating ecological restorations (Ruiz-Jaen & Aide, 342 2005; Wortley et al. 2013), to our knowledge, there are not simplified methodologies 343 readily available for practitioners, that give information about ecosystem services and 344 assess the decision-making process. Landscape Function Analysis methodology 345 (Tongway and Hindley, 2004) is a methodology that fits with these objectives; however 346 it is impractical for a non-scientific public due to its complexity. Other studies also take 347 a similar approach to RESTOQUARRY (Comín et al. 2018; Derhé et al. 2016; Lithgow 348 et al. 2015; Bulloch et al. 2011; Birch et al. (2010)), taking into consideration the 349 provision of ecosystem services and/or the ecosystem functions, but at a larger scale, with 350 different target reference sites, and more focused on planning restorations than on 351 evaluating the executed ones. While these other studies are focused on ecosystem services 352 provided by ecological restoration in a general way (Comín et al. 2018; Bulloch et al. 353 2011; Birch et al. 2010), these works do not address the measure of some field parameters 354 directly linked to the quantification of ecosystem services (i.e. carbon storage, nutrient 355 cycling, water regulation, biomass production), as are made by RESTOQUARRY for 356 evaluating restoration success. On the other hand, only a few studies are focused on the 357 particular issue of the evaluation of mine restorations (Courtney et al. 2010; Dzwonko 358 and Loster 2007), and they mainly assess very specific indicators related to soil 359 rehabilitation or vegetation recover. Another differential characteristic of 360 RESTOQUARRY is that includes zone specific indicators (geotechnical risk, drainage 361 network, soil quality and degradation, vegetation structure and diversity) adapted to the 362 specificities of mine restoration, such as the need of constructing a drainage network or 363 creating a new soil layer (technosol). 364 365 4.2 Links between the current procedure of quarries control and the RESTOQUARRY 366 protocol 367 Mine restoration evaluation tests should assure the correct restoration of mine sites and 368 the recovery of the financial guarantees posted by mine companies conditioned to 369 obtaining satisfactory results in these tests. This evaluation scheme is adopted in some 370 countries like Canada (Mining Act), USA (Surface Mining Act), or the European Union 371 (Directive 2006/21CE). In Spain, for example, the transposition of the EU Directive 372 2006/21/CE (RD 975/2009) established the need to monitor restorations works each year, 373 until the end of the guarantee period. According to this law, the monitoring process could 374 be done directly by competent administration officers or by accredited external 375 companies. Currently, sincethe evaluation protocols, indicators, and reference values are 376 not provided, the assessment result depends on the criteria of the evaluator, which 377 sometimes varies according to its background. In this context, RESTOQUARRY protocol 378 is a more accessible tool for a non-scientific public that could help to objectify and 379 standardize the evaluation process, enhancing its transparency for administration bodies, 380 companies, and citizens. 381 382 4.3 Methodological limitations 383 A limitation of the global RQI could be that it is confusing if it is not accompanied by an 384 interpretation of the RQx partial values. The fact that a wide range of indicators is 385 considered makes it difficult to obtain low RQI values despite the fact that some RQx 386 could be very low or even 0, leading to relatively high global RQI values for restorations 387 even though they may have critical faults. We propose the consideration of key indicators 388 in order to decide the adoption of corrective measures could help to solve this problem. 389 Other methodologies for evaluation (Lithgow et al. 2015) have used a similar 390 approximation (hierarchical grouping) to prioritize among indicators, obtaining 391 satisfactory results. However, by using the current criterion for key indicators definition 392 (weight higher than 2%), more than a half of them are considered key indicators, which 393 may be excessive. This criterion could be redefined in order to reduce the number of key 394 indicators; however this will increase the chances that some poor quality restorations pass 395 the assessment. 396 The RESTOQUARRY protocol has been designed and tested mainly in Mediterranean 397 quarries, therefore its application in other climes or mine types could present mismatches 398 in some indicators and reference values. Moreover, this protocol is not a suitable tool for 399 evaluating very case-specific restorations, targeting singular habitats or species 400 (endangered and/or protected) where an expert knowledge is needed. In these cases, some 401 indicators and reference values included in the RESTOQUARRY could not be 402 appropriate, or, alternative indicators should be evaluated. For the same reason, 403 RESTOQUARRY may not be appropriate for evaluating agricultural restorations, but in 404 these cases, the protocol could be easily adapted to specific goals by changing the set of 405 indicators while preserving the general scheme. 406 407 Conclusions 408 The RESTOQUARRY protocol was designed to help mine companies, competent 409 administration and accredited monitoring consultancies in the process of evaluating 410 ecological restoration of mine sites. It consists of a multifactorial procedure, including 411 selected expert-weighted indicators, that allows its large-scale application in the context 412 of ecological restoration of Mediterranean quarries. The protocol could support mine 413 companies in the decision-making process to select corrective measures for improving 414 and optimizing the restoration process. At the same time, it could be useful for competent 415 administration bodies to approve the return of restoration financial guarantees. In 416 summary, RESTOQUARRY is a tool that can contribute to improve the practice and the 417 monitoring of ecological restoration of mine sites. 418 419 Acknowledgements 420 This study was financed by the Catalan Government through the project “Research and 421 Innovation in the process and control of extractive activities restoration”. Authors thank 422 the members of the expert panel: Esteve Serra (Generalitat de Catalunya), Montserrat 423 Pedra (Generalitat de Catalunya), Jordi Cortina (Universitat d’Alacant), Albert Solé 424 (Estación Experimental de Zonas Áridas-CSIC), Ramon Josa (Universitat Politècnica de 425 Catalunya), David Badia (Universidad de Zaragoza), Montserrat Jorba (Universitat de 426 Barcelona), Rosa Poch (Universitat de Lleida), Miquel Arán (Eurofins), Tomàs Carbó 427 (Carbó Enginyers, SL), Juan Bautista Menéndez (Universitat Politècnica de Catalunya), 428 Joan Pous (UNILAND), Fernando González (ARICEMEX), Xavier Foj, Manuel Juan 429 (KNAUF) and Carles Ventura (PROMSA). 430 431 432 References 433 Alcañiz, J.M., Ortiz, O., Carabassa, V., 2008. Utilización de lodos de depuradora en 434 restauración. Manual de aplicación en actividades extractivas y terrenos 435 marginales. Agencia Catalana del Agua, Generalitat de Catalunya, Barcelona, 114 436 p. 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Zones are described in this work as homogeneous 592 portions of the whole restored area. 593 ZONE INDICATORS Geotechnical risk Erosion/physical Drainage Soil quality Vegetation status degradation network and functionality Maximum diameter Area affected by Drainage Soil depth (m) Plant cover (%) of fallen blocks (m) rill erosion (% channels divided into: related to the broken Particles <2 herbaceous cover and Area affected by total area) (% of total mm (g kg-1) woody species fallen blocks (% of channels) (shrubs and trees) the total area) Estimated rill Clay content cover erosion rates Drainage (g kg-1) Area affected by (Mg ha-1 year-1) channels Area occupied by landslides (% of the filling-in Organic exotic/invasive total area) Rain splash (% of total matter (g kg-1) species (% of the protection (% of channels) total area) Other signs of the surface Carbonates (g instability: cracks, protected) Drainage kg-1) Species with fruits subsidence, network (number of species) deformations, faults, Surface crusts functionality Electrical fallen trees presence (% of conductivity, Mortality of planted (qualitative) (qualitative) damaged, 1:5 extract (dS woody species (%) stabilized and m-1) Sheet erosion non- Woody species (qualitative) functional Soil pH richness channels) (% related to Piping or Total nitrogen richness on reference subsurface flows (%) site) (qualitative) Available Woody species phosphorous density (% related to (mg kg-1) density in reference site, per species) Available potassium Woody species (mg kg-1) recruited (number) Physical Herbaceous species contaminants richness (% related presence to richness on (number of reference site) elements observed) 594 Table 2. Pre-selection of restoration quality area indicators included in the preliminary 595 proposal of evaluation protocol. AREA INDICATORS Landscape integration Ecological connectivity and Anthropic impacts fauna presence Chromatic and textural Ecological barriers Uncontrolled vehicle integration (presence and type) circulation (qualitative) (qualitative) Woody plants with edible fruits Geomorphic integration (Species and density) Waste dumping (qualitative) (type, magnitude and Fauna refuges/supply structures distribution) Internal road networks (presence) (functionality, density and Grazing width) Fauna observations (presence and (number and species) intensity) Fauna paths Abandoned (presence) constructions and facilities Fauna traces (presence, magnitude (presence) and height) Nests (presence) Burrows (presence) 596 597 598 Table 3. Geological substrates and ranges of precipitation and air temperature in a 599 representative selection of the extractive activities included in the pilot test (n=55). Dominant lithology Precipitation Mean annual air (n=number of Dominant mineralogy rank temperature activities included) (mm/year) rank (ºC) Limestone (24) Carbonatic 526-747 14.1-16.1 Gravel (9) Mixed 416-799 13.1-15.2 Lignite (6) Carbonatic 408-888 10.6-15.8 Sand and clay (6) Siliceous and carbonatic 506-795 14.8-15.6 Evaporites (4) Gypsic, saline and carbonatic 585-793 13.2-14.6 Basalt (2) Siliceous 685-745 15.8-16.2 Weathered granite (2) Siliceous 653-753 15.1-16.3 Granite (2) Siliceous 599-613 13.8-15.3 600 601 602 Table 4. Results for substrate quality indicators on the evaluated zones. *Data refer to 603 <2mm soil fraction. Soil depth Particles <2 Clay content EC, 1:5 extract pH* (m) mm (%) (%)* (dS m-1)* Average 22 44 24 0.4 8.0 Max. 50 94 50 2.2 8.8 Min. 0 19 6 0.1 6.5 Median 20 42 23 0.2 8.0 Standard 22 19 10 0.5 0.3 deviation Carbonates Organic Available P Available K Total N (%)* (%)* matter (%)* (mg kg-1)* (mg kg-1)* Average 22 2.6 0.14 33 217 Max. 58 12.4 0.57 199 972 Min. 0 0.2 0.02 2 38 Median 23 1.9 0.10 19 148 Standard 15 2.2 0.11 42 184 deviation 604 605 606 Table 5. Weight of the selected indicators according to their importance for restoration 607 success measurement after pairwise comparison by experts panel members. *key 608 indicators. GROUP INDICATOR GROUP WEIGHT INDICATOR WEIGHT (%) (%) Area affected by landslides* 9.9 Geotechnical risk 18.0 Area affected by fallen blocks* 4.7 Other signs of instability* 3.4 Rain splash protection* 4.5 Erosion and physical Area affected by concentrate erosion* 4.3 degradation 15.3 Estimated erosion rates* 3.7 Other degradation processes* 2.8 Drainage channels broken* 7.7 Drainage network 15.0 Drainage channels filling* 3.9 Drainage network functionality* 3.4 Soil depth* 2.4 Particles <2 mm content* 2.5 Texture 1.9 Soil quality 14.3 Organic matter / Nitrogen* 2.4 Electrical conductivity, 1:5 extract 2.0 pH / Phosphorous / Potassium 2.0 Impurities (glass, plastics, metals, etc.) 1.1 Plant cover* 2.9 Woody species richness* 2.6 Vegetation status and Woody species density 2.0 functionality 12.7 Woody species recruitment 1.7 Area occupied by exotic/invasive species 1.7 Herbaceous species richness 1.8 Chromatic and textural integration* 3.1 Landscape integration 12.0 Geomorphologic integration* 7,2 Road network 1.7 Ecological barriers* 2.1 Ecological Woody plants with edible fruits 1.3 connectivity and 6.4 Fauna refuges/supply structures 1.1 fauna presence Fauna observations 1.9 Uncontrolled vehicle circulation 1.6 Waste dumping* 2.4 Anthropic impacts 6.3 Grazing 1.0 Abandoned constructions and facilities 1.3 609 610 611 612 613 Table 6. Example of RQI index calculation for a quarry evaluated using the 614 RESTOQUARRY protocol. Critical indicators warning: RQx < 0,5 for key indicators 615 (weight more than 2%) or RQx = 0 for any indicator. CRITICAL GROUP INDICATOR RQx RQIx INDICATORS Area affected by landslides 1.0 9.9 Geotechnical risk Area affected by fallen blocks 1.0 4.7 Other signs of instability 1.0 3.4 Erosion and Rain splash protection 1.0 4.5 physical Area affected by rill erosion 1.0 4.3 degradation Estimated erosion rates 1.0 3.7 Other degradation processes 0.9 2.5 Drainage channels broken 1.0 7.7 Drainage network Drainage channels filling 1.0 3.9 Drainage network functionality 1.0 3.4 Soil depth 0.2 0.5 WARNING Particles <2 mm content 1.0 2.5 Texture 1.0 1.9 Soil quality Organic matter / Nitrogen 0.6 1.5 Electrical conductivity, 1:5 extract 1.0 2.0 pH / Phosphorous / Potassium 0.2 0.3 Physical pollutants 0.9 1.0 Plant cover 1.0 2.9 Vegetation status Woody species richness 0.2 0.5 WARNING and Woody species density 0.9 1.9 functionality Woody species recruitment 1.0 1.8 Area occupied by exotic/invasive species 1.0 1.7 Herbaceous species richness 1.0 1.7 Chromatic and textural integration 0.3 0.8 WARNING Landscape Geomorphologic integration 1.0 7.2 integration Road network 1.0 1.7 Ecological barriers 1.0 2.1 Ecological Woody plants with fruits 0.0 0.0 WARNING connectivity and Fauna refuges/supply structures 1.0 1.1 fauna presence Fauna observations 1.0 1.9 Uncontrolled vehicle circulation 1.0 1.6 Waste dumping 0.5 1.3 Anthropic impacts Grazing 0.0 0.0 WARNING Abandoned constructions and facilities 1.0 1.3 Recommendation: bond return dependent on RQI = 87 adoption of corrective measures 616 Table 1. Pre-selection of restoration quality zone indicators included in the preliminary 617 proposal of evaluation protocol. Zones are described in this work as homogeneous 618 portions of the whole restored area. 619 ZONE INDICATORS Geotechnical risk Erosion/physical Drainage Soil quality Vegetation status degradation network and functionality Maximum diameter Area affected by Drainage Soil depth (m) Plant cover (%) of fallen blocks (m) rill erosion (% channels divided into: related to the broken Particles <2 herbaceous cover and Area affected by total area) (% of total mm (g kg-1) woody species fallen blocks (% of channels) (shrubs and trees) the total area) Estimated rill Clay content cover erosion rates Drainage (g kg-1) Area affected by (Mg ha-1 year-1) channels Area occupied by landslides (% of the filling-in Organic exotic/invasive total area) Rain splash (% of total matter (g kg-1) species (% of the protection (% of channels) total area) Other signs of the surface Carbonates (g instability: cracks, protected) Drainage kg-1) Species with fruits subsidence, network (number of species) deformations, faults, Surface crusts functionality Electrical fallen trees presence (% of conductivity, Mortality of planted (qualitative) (qualitative) damaged, 1:5 extract (dS woody species (%) stabilized and m-1) Sheet erosion non- Woody species (qualitative) functional Soil pH richness channels) (% related to Piping or Total nitrogen richness on reference subsurface flows (%) site) (qualitative) Available Woody species phosphorous density (% related to (mg kg-1) density in reference site, per species) Available potassium Woody species (mg kg-1) recruited (number) Physical Herbaceous species contaminants richness (% related presence to richness on (number of reference site) elements observed) 620 621 622 Table 2 AREA INDICATORS Landscape integration Ecological connectivity and Anthropic impacts fauna presence Chromatic and textural Ecological barriers Uncontrolled vehicle integration (presence and type) circulation (qualitative) (qualitative) Woody plants with edible fruits Geomorphic integration (Species and density) Waste dumping (qualitative) (type, magnitude and Fauna refuges/supply structures distribution) Internal road networks (presence) (functionality, density and Grazing width) Fauna observations (presence and (number and species) intensity) Fauna paths Abandoned (presence) constructions and facilities Fauna traces (presence, magnitude (presence) and height) Nests (presence) Burrows (presence) 623 624 625 Table 3 Dominant lithology Precipitation Mean annual air (n=number of Dominant mineralogy rank temperature activities included) (mm/year) rank (ºC) Limestone (24) Carbonatic 526-747 14.1-16.1 Gravel (9) Mixed 416-799 13.1-15.2 Lignite (6) Carbonatic 408-888 10.6-15.8 Sand and clay (6) Siliceous and carbonatic 506-795 14.8-15.6 Evaporites (4) Gypsic, saline and carbonatic 585-793 13.2-14.6 Basalt (2) Siliceous 685-745 15.8-16.2 Weathered granite (2) Siliceous 653-753 15.1-16.3 Granite (2) Siliceous 599-613 13.8-15.3 626 627 628 Table 4 Soil depth Particles <2 Clay content EC, 1:5 extract pH* (m) mm (%) (%)* (dS m-1)* Average 22 44 24 0.4 8.0 Max. 50 94 50 2.2 8.8 Min. 0 19 6 0.1 6.5 Median 20 42 23 0.2 8.0 Standard 22 19 10 0.5 0.3 deviation Carbonates Organic Available P Available K Total N (%)* (%)* matter (%)* (mg kg-1)* (mg kg-1)* Average 22 2.6 0.14 33 217 Max. 58 12.4 0.57 199 972 Min. 0 0.2 0.02 2 38 Median 23 1.9 0.10 19 148 Standard 15 2.2 0.11 42 184 deviation 629 630 631 Table 5 GROUP INDICATOR GROUP WEIGHT INDICATOR WEIGHT (%) (%) Area affected by landslides* 9.9 Geotechnical risk 18.0 Area affected by fallen blocks* 4.7 Other signs of instability* 3.4 Rain splash protection* 4.5 Erosion and physical Area affected by concentrate erosion* 4.3 degradation 15.3 Estimated erosion rates* 3.7 Other degradation processes* 2.8 Drainage channels broken* 7.7 Drainage network 15.0 Drainage channels filling* 3.9 Drainage network functionality* 3.4 Soil depth* 2.4 Particles <2 mm content* 2.5 Texture 1.9 Soil quality 14.3 Organic matter / Nitrogen* 2.4 Electrical conductivity, 1:5 extract 2.0 pH / Phosphorous / Potassium 2.0 Impurities (glass, plastics, metals, etc.) 1.1 Plant cover* 2.9 Woody species richness* 2.6 Vegetation status and Woody species density 2.0 functionality 12.7 Woody species recruitment 1.7 Area occupied by exotic/invasive species 1.7 Herbaceous species richness 1.8 Chromatic and textural integration* 3.1 Landscape integration 12.0 Geomorphologic integration* 7,2 Road network 1.7 Ecological barriers* 2.1 Ecological Woody plants with edible fruits 1.3 connectivity and 6.4 Fauna refuges/supply structures 1.1 fauna presence Fauna observations 1.9 Uncontrolled vehicle circulation 1.6 Waste dumping* 2.4 Anthropic impacts 6.3 Grazing 1.0 Abandoned constructions and facilities 1.3 632 633 634 635 636 Table 6 637 CRITICAL GROUP INDICATOR RQx RQIx INDICATORS Area affected by landslides 1.0 9.9 Geotechnical risk Area affected by fallen blocks 1.0 4.7 Other signs of instability 1.0 3.4 Erosion and Rain splash protection 1.0 4.5 physical Area affected by rill erosion 1.0 4.3 degradation Estimated erosion rates 1.0 3.7 Other degradation processes 0.9 2.5 Drainage channels broken 1.0 7.7 Drainage network Drainage channels filling 1.0 3.9 Drainage network functionality 1.0 3.4 Soil depth 0.2 0.5 WARNING Particles <2 mm content 1.0 2.5 Texture 1.0 1.9 Soil quality Organic matter / Nitrogen 0.6 1.5 Electrical conductivity, 1:5 extract 1.0 2.0 pH / Phosphorous / Potassium 0.2 0.3 Physical pollutants 0.9 1.0 Plant cover 1.0 2.9 Vegetation status Woody species richness 0.2 0.5 WARNING and Woody species density 0.9 1.9 functionality Woody species recruitment 1.0 1.8 Area occupied by exotic/invasive species 1.0 1.7 Herbaceous species richness 1.0 1.7 Chromatic and textural integration 0.3 0.8 WARNING Landscape Geomorphologic integration 1.0 7.2 integration Road network 1.0 1.7 Ecological barriers 1.0 2.1 Ecological Woody plants with fruits 0.0 0.0 WARNING connectivity and Fauna refuges/supply structures 1.0 1.1 fauna presence Fauna observations 1.0 1.9 Uncontrolled vehicle circulation 1.0 1.6 Waste dumping 0.5 1.3 Anthropic impacts Grazing 0.0 0.0 WARNING Abandoned constructions and facilities 1.0 1.3 Recommendation: bond return dependent on RQI = 87 adoption of corrective measures 638 639 640 FIGURES 641 642 643 644 Figure 1. Functional curves for some soil parameters: (a) soil depth, (b) particles < 2 mm, 645 (c) clay content, (d) lime content, (e) organic matter, (f) total nitrogen. RQx= restoration 646 quality value for the respective parameter. 647 648 649 650 Figure 2. Geographical distribution of restored mining activities evaluated applying the 651 RESTOQUARRY methodology, in the NE Iberian Peninsula. 652 653 654 655 656 Figure 3. Differences in vegetation type between restored zones and surrounding areas 657 (left), and the presence of artificial morphologies, like walls (cliffs) in flat/hilly 658 landscapes (right), that make the integration of the restored areas to the landscape 659 difficult. 660 661 662 663 Figure 4. The presence of abandoned buildings and machinery of the former extractive 664 activity has a negative impact on the integration of the restored areas and represents a risk 665 for people. 666