Are we approaching tipping points with regard to the interwoven physical, biological, geochemical, and human dynamics of Earth’s skin? What is the state of Earth’s critical zone, the surface and near-surface region of Earth where life persists? How can observed changes in Earth’s climate and biota help us make better decisions in the Anthropocene—the age of humans?
Human activities are rapidly changing Earth’s surface [Hooke, 2000; Wilkinson, 2005] and its ecological and biogeochemical systems. These anthropogenic effects have consequences that will persist or deepen with time. For example, carbon dioxide levels in the atmosphere have recently surpassed 400 parts per million, the highest in several million years, and these elevated levels and their consequences will persist for many millennia to come.
Effects of this rise include diminished glaciers, thawed permafrost, higher sea levels, drowned coastal land, and acidified oceans. Population growth and changing land use are stressing freshwater resources [Ferguson and Gleeson, 2012]. In much of the world, agriculture and development have markedly changed the flow of sediment and nutrients, polluting rivers, lakes, and coastal ecosystems with fertilizers [Syvitski et al., 2005; Tilman et al., 2001].
These various stressors interact in complex ways [Thornton et al., 2007]. However, attempts to quantify a baseline or monitor effects of these ongoing changes have been limited in geographic extent and the range of variables and processes that they consider. Recently, the National Science Foundation (NSF) tasked a subset of the Earth surface process community to brainstorm how a targeted investment of research and infrastructure might address this challenge.
Since September 2014, the group has been developing an initiative to capture the past, present, and future status of Earth’s surface systems—the pulse of the planet. Here we describe that vision and seek broad community input.
The Earth Surface Observatory
To predict how Earth’s surface and climate will change—and to improve decision making—it’s pivotal to map the critical zone across entire continents and reconstruct Earth’s paleoclimates during times of major change in geologic history. With planning and vision, we can achieve this goal within several decades.
As a first step, we propose a 10-year Earth Surface Observatory initiative, consisting of three complementary components. First, a Paleoenvironmental Reconstruction Program will help us understand how Earth’s surface responded to past perturbations. Second, an Earth Rover campaign will characterize the present state of the critical zone. Third, a Distributed Analytical and Experimental Laboratory Network will provide scientists open access to existing and future cutting-edge analytical and experimental facilities.
Together, these three components represent a holistic approach to capturing the past, present, and future pulse of Earth’s surface systems. This infrastructure would better equip the community to address the research priorities that the National Academy of Sciences has laid out in several reports and white papers (available from the National Academies Press):
- Landscapes on the Edge (2010)
- Understanding Earth’s Deep Past: Lessons for our Climate Future (2011)
- New Research Opportunities in the Earth Sciences (2012)
- Challenges and Opportunities in the Hydrologic Sciences (2012)
The Earth Surface Observatory Initiative builds upon and leverages existing NSF-funded projects yet goes beyond those efforts in its goals of understanding deep time processes and achieving continental-scale data products to open vast new realms of inductive inquiry.
Tapping the Earth’s Archives
The Earth has now entered the Anthropocene, the geologic epoch in which humans are altering the Earth’s ecosystems to an unprecedented extent. This plunge into uncharted territory highlights the need to tap Earth’s archive of natural experiments—the stratigraphic and paleontologic record, which documents how different Earth systems have responded to past climate change.
One of the best ways to assess risk and predict changes to Earth’s surface and climate systems is by knowing what contributed to resilience and sensitivity of landscapes, environments, and ecosystems in the past. To accomplish this, we need a concerted effort to reconstruct Earth’s environments at key windows in geologic history—the Paleoenvironmental Reconstruction Program component of this effort.
We propose a coordinated program, based primarily on continental drilling, to investigate rock records, targeting periods when Earth’s surface systems underwent dynamic change. These episodes of environmental upheaval can serve as “distant mirrors” [Tuchman, 1987] for our own times. These drill cores, along with other geological data collected on site, will allow us to reconstruct a detailed picture of how Earth’s biological, geochemical, and geophysical systems responded to significant historical climate changes.
The goal is to organize diverse, interdisciplinary efforts around common themes and time intervals. This initiative would also address the urgent need for infrastructure by providing access to drilling rigs, designating a centralized location to curate recovered cores, and expanding access to state-of-the-art analytical facilities for core analysis.
Exploring Planet Earth
Quantifying environment parameters such as the movement of water, sediment, and solutes is key to understanding Earth dynamics [Anderson et al., 2004]. But in order to understand how they change at a continental level, we first need a common set of baseline measurements across a wide range of climates and geology. These will calibrate remote sensing products for the continental mapping initiative and also serve as inputs for predictive Earth systems models.
Our proposed Earth Rover campaign spans all of the United States’ 25 physiographic provinces, with urban, rural, and agricultural sites (about 75 sites total). This campaign will yield information about the relevant geologic, geophysical, geochemical, hydrologic, and biotic properties and the deep history of the critical zone. Within each physiographic province, we will choose sites on the basis of geology and vegetation, leveraging efforts at existing long-term observatories.
Field data collection efforts would feature “Earth rover” vehicles with cutting-edge instrumentation that perform a common set of measurements at each site. These rovers will move from site to site, collecting data using methods that are too expensive or labor intensive to be practical for long-term monitoring at fixed instrumentation sites.
We will monitor each site for 10 years in an approach with four phases. During phase 1 (years 1–3), airborne sensors will map the area using lidar, hyperspectral, thermal, reflectance, gravity, magnetics, time domain electromagnetic, and geochemical data. The resulting data will then serve as inputs to site-based models of Earth surface processes in phase 2.
The first two phases will inform experimental design for subsequent intensive data collection over several weeks at each site using a dedicated mobile Earth rover unit (phase 3; years 2–6). The rovers will measure biotic and abiotic properties and track the movement of moisture and nutrients through the atmosphere, surface, and underground.
These data will be used as a baseline to calibrate remote sensing algorithms and develop relationships among remote sensing products (e.g., thermal and reflectance-based imagery) and other critical zone properties (e.g., soil moisture). In phase 4, beginning in year 5, another rover will return to a subset of sites to characterize time-sensitive responses to infrequent events (e.g., fire, storms, land use changes) or seasonal changes.
An Accessible Network of Laboratories
In addition to the wealth of new data that the rovers will collect, we also propose a complementary investment in laboratories and facilities—the Distributed Analytical and Experimental Laboratory Network component. Experiments and high-precision analyses of Earth materials are important tools for understanding Earth surface processes, biogeochemical systems, and the critical zone. This initiative will broadly integrate and expand access to manipulative experiments and high-cost analytical work that are fundamental to synthesizing field and theoretical efforts to understand Earth surface processes.
Building on the success of existing laboratory networks such as the National Nanotechnology Coordinated Infrastructure program, we envision a concerted effort to link and improve existing facilities, as well as a distributed network of six new “full-spectrum” laboratories, each with a scope reaching from the benchtop to the field and from the nanoscale to the landscape scale. Facilities will work with the Earth Rover field campaign and the Paleoenvironmental Reconstruction Program and link researchers across Earth surface subfields, including microbiology, geochemistry, sedimentology, geomorphology, ecology, and hydrology.
Reaching Out for Feedback
This three-pronged infrastructure investment is necessary to comprehensively assess the sensitivity of Earth’s surface to future climate and land use changes and to manage risks to our critical zone habitat. These three components will also provide an abundance of opportunities for training, outreach, and research coordination, including distributing inexpensive sensors to citizen-scientists, schoolyard partnerships with the Earth Rover campaign and Paleoenvironmental Reconstruction Program, and teacher-training programs run by funded staff members.
We invite the community to leave comments on this article online. Specifically, we seek suggestions for how this initiative might be best integrated into existing centers and programs for data collection and dissemination such as the NSF Critical Zone Observatories and EarthCube.
This article is the outcome of an NSF-funded meeting to discuss research infrastructure in support of NSF surface Earth processes grand challenges. The following individuals also attended the meeting and contributed to the ideas in this article: Jose Cerrato, Marjorie Chan, Gordon Grant, Steve Holbrook, Clark Johnson, Ellen Martin, Kamini Singha, Dena Smith, and Scott Tyler.