The Humpty Dumpty Effect on Planet Earth

Humans have treated the earth harshly. Degradation of extant ecosystems leaves little chance that they might function as they have in the past. Putting back the pieces and restoring what once existed is no longer possible even with re-wildling—an effect analogous to the Humpty Dumpty parable. However, we do have conservation successes after concerted efforts related to habitat protection, species and ecosystem restoration, and planning. While the changes to Earth's biosphere are grave, necessitating immediate and exhaustive action, our Humpty Dumpty world reassembles with progressive conservation victories at all regional scales from local to global which should lead to a modicum of optimism rather than despair. We suggest that to be truly effective our work as academic scientists must be more than publishing in scholarly journals. At the least, this should include changes in how success is measured in science and how university tenure is awarded.


INTRODUCTION
Many know the sad fate of Humpty Dumpty. He sat on a wall and had a great fall. Depicted as a fragile egg, the nineteenth century British allegory unfolds a story in which all the kings' horses and all the kings' men could not put Humtpy back together again. We suggest that an Anthropocene version of this parable is our fragile biosphere.
We all know that human-induced disassembly of biodiversity and restructuring of ecological relationships have resulted in fundamental planetary changes. While Earth will always be the sum of its ecological processes, these processes differ from those existing even a decade ago. Just as Humpty could not be reconstituted into his pre-fall form, we are not likely to reconfigure biotic assemblages into their previous forms, despite rewilding and restoration efforts (Navarro and Pereira, 2015;Noss, 2020). Most places are just changed. We argue, however, that we do not have the luxury to lament this Humpty Dumpty Effect (Figure 1). We need to acknowledge it and use it to galvanize our tactics, not cripple us with a yearning for the past.
We both bristled when Chris Thomas's provocative and beautifully written "Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction" appeared in 2017. Neither of us was prepared to become resigned to a new version of Earth. We did not accept the premise that we need to mourn and carry on. But we must. Yesterday's world is not today's nor tomorrow's. With this in mind, we recently published a paper on food web disassembly that contextualizes how unabated human population growth is a central, though not the sole, ecological disruptor of most large mammal communities (Berger et al., 2020). Our central thesis was that the world is messy, that the pieces cannot be put back together, and that ecological transitions in the form of regime shifts, thresholds, and tipping points (Holling, 1973(Holling, , 1986Berlow et al., 2012) are expanding globally. A major take home point of this paper was steeped in the reality of accepting biological change, a topic central in Inheritors of the Earth (Thomas, 2017). Our paper rings with words of grave acceptance, though acceptance need not be passive nor contraindicate optimism.
We remain sanguine because of success stories that provide precedents for ways forward. These successes understandably vary, ranging from local to global and of broad thematic significance to small local victory. For instance, in addition to the vast protected areas with ecosystems functioning much in the way of the past-albeit situated in high-latitude regions with low human density (e.g., Tibet's Chang Tang, Northeast Greenland National Park, Alaska's Wrangell-St. Elias, and Russia's Arctic National Park)-governments and non-governmental organizations have also invested in protected areas at lower latitudes (e.g., Serengeti, Madidi, and Yellowstone National Parks; Kennedy et al., 2019).
Examples of other successes across the globe are presented in Table 1. Rewilding via species reintroduction has proven a particularly valuable tool at broad landscape levels. The reintroduction of gray wolves (Canis lupus) into the northern Rocky Mountains of Wyoming and Idaho re-established prey fear responses and former trophic interactions (Estes et al., 2012). Other examples of highly successful reintroductions include water buffalo (Bubalus bubalis) back into the Danube River Delta, Ukraine, red kite (Milvus milvus) into Britain, and bandicoot (Isoodon obesulus) and bilby (Macrotis lagotis) into Australia (Moseby and O'donnell, 2003;Cogȃlniceanu, 2012;Legge et al., 2018). Lesser-known successes have been removal of railroad fencing and creation of over-and underpasses-human actions that have reinstated migratory pathways. In Mongolia's Gobi Desert, for example, khulan (Equus hemionus), now pass on both sides of a modified railroad impediment for the first time in six decades (News Wise, 2020).
We write in full cognizance of the biodiversity extinction crisis and that we are losing more species than we are recovering (Nicholson and Possingham, 2007;Kolbert, 2014). Indeed, under our current circumstances of limiting funding and resources, a tactic of conservation triage prevails (Hayward and Castley, 2018). Yet, triumphs do still occur and do so because of individual choices and institutional action-both of which are the result of labile sociocultural-political processes that can change within a generation. Scientific advances, such as those offered by the nascent but growing field of synthetic biology, can bolster such changes (Redford and Adams, 2021). Other sources of cautious optimism include more efficient urban planning, the leveraging of high-resolution geospatial data to address agricultural demands, greater opportunities for reproductive choice by women, and a decrease in the intrinsic rate of human population growth globally (Sanderson et al., 2018;Vollset et al., 2020;ACF, 2021). Calls to action, especially when voiced across generations, gender, and ethnicity solidifies support and can result in change. To wit: the civil unrest related to environmental (in)justice garnered by Greta Thunberg (Rodrick, 2020).
We believe emphatically that as academic scientists we cannot limit ourselves to the currency of our trade: peerreviewed publications. Essays or perspectives do not accomplish conservation, nor do they typically reach the public (Strother and Fazal, 2011;Morrison et al., 2018). We must work where we can to influence decision-makers and to implement sociocultural change related to environmental policy. This involves non-academic pursuits such as working with agencies   Berger and Wehausen (1991) and Berger et al. (2020). c Sullivan et al. (2007). d Mara (2019) and Veldhuis et al. (2019). e Maekawa et al. (2013) and Robbins et al. (2011). f Birdlife (2017). g Kimbrough (2020). h Nguyen et al. (2019). i Anonymous (2008) and Sithirith (2015). j Tompkins (2019). k Travaini et al. (2015) and Gelin et al. (2017). l ABC Birds (2016). m Cogȃlniceanu (2012). n Royal Society (2020). o Rodríguez and Calzada (2015). p Legge et al. (2018). q Moseby and O'donnell (2003) and Guardian (2019). and policymakers, writing opinion editorials, working toward gender equity, engaging in complicated conversations with multiple stakeholders, and acknowledging iterative, structural racism that has profound impacts for environmental justice. Such actions are requisite to enact broad conservation changes (Wittemyer et al., 2018). Though work beyond academia (e.g., outreach, advocacy) is often not rewarded at institutions of higher education, standards are readily changed by re-writing the requirements for tenure.
In the end, we can't look backwards. Ecological restoration and rewilding will not bring us back to what Earth once was, even in the recent past (Thomas, 2017;Berger, 2018;Berger et al., 2020). But new versions will coalesce and while we may not gain identical species assemblages, we can work toward comparable ecological function (Chazdon, 2014). Working at all scales, we too can invest in where, when and how we try to impact a world we'd like to see.

DATA AVAILABILITY STATEMENT
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

AUTHOR CONTRIBUTIONS
All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.

FUNDING
This study was funded by Colorado State University, the Wildlife Conversation Society, and the University of Colorado.