# Assessing the Functional Response to Streamside Fencing of Pastoral Waikato Streams, New Zealand
## 1 Introduction  
Concerns about stream degradation have led to increasing efforts worldwide over the last two decades to restore these ecosystems [1; 2]. It is estimated that over US$1 billion is spent annually on various aquatic habitat rehabilitation activities in the United States alone [1] and similar efforts are underway in Europe to rehabilitate and reconnect river habitats, such as the Skjern ($37.7 million total project cost for largest river system in Denmark) [3], Rhine ($4.4 billion total project costs; Germany) [4] and Danube River basins ($6 billion total project cost; ten European countries) [5]. A large variety of restoration techniques are applied to mitigate and reverse human impacts on rivers and streams. Fencing of waterways, for example, is a common restoration approach in New Zealand, and generally occurs in pastoral land to exclude livestock from streams, thereby reducing bank erosion and direct faecal bacteria input [6]. Once fenced, stream banks are often replanted to accelerate the re-establishment of riparian vegetation. As riparian vegetation grows over time, stream health is expected to improve due to lower water temperatures from shade, reduced nutrient, sediment and faecal bacteria input, and increased habitat provision for aquatic and riparian biota [7; 8; 9]. Understanding the effectiveness of stream restoration techniques is critical for the cost-effective design and implementation of future restoration efforts. However, the environmental outcomes of stream restoration projects are rarely evaluated. [PERSON] et al. [PERSON] et al. (2018) found that only 10% of \(\approx\)3700 reviewed restoration projects in the United States recorded some form of assessment or monitoring, and if restoration measures were monitored, evaluations were highly subjective, rather than based on robust scientific measures. In a more recent international review of 644 restoration projects, [PERSON] et al. [PERSON] et al. (2018) noted that when indicators of riverine attributes were measured, results were highly variable and dependent on the restoration technique and the indicators measured. For example, successful outcomes were most often recorded when riparian management was the focus of restoration and physical habitat, biophysical processes and benthic communities were the focus of assessment [PERSON] et al. (2018). A lack of robust post restoration assessments, due to inconsistent or incomplete indicators for example, hinders the public and scientific community from learning from successes and failures, and thus from improving future practices [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). Stream restoration is further complicated by temporal and spatial variation in drivers of stream health, including disturbance regimes, which can lead to hysteresis or slow recovery over time and multiple recovery pathways and endpoints [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). Restoration hysteresis describes when the recovery pathway is different to the degradation pathway and may occur when feedback mechanisms that hold an ecosystem in a certain state are not fully addressed by restoration techniques ([PERSON], 2009). Therefore, active stream restoration, such as large wood addition, e.g., [PERSON] et al. [PERSON] et al. (2018), in addition to passive stream restoration (such as streamside fencing) may be required to overcome restoration hysteresis. Alternative recovery trajectories include the 'rubber band' model where recovery follows closely the degradation pathway, the 'humpty-dumpty' model where recovery can result in various endpoints that are distinct from the pre-degraded condition, and the'shifting target model' where both the recovery pathway and endpoint are unpredictable [PERSON] et al. (2018). Assessing stream restoration at any single point in time without knowing the nature of the recovery pathway could provide an inaccurate assessment of restoration success.