# Exploring a Moderate Fallow Scale of Cultivated Land in China from the Perspective of Food Security
## 4 Results
### Lost GPP of Cultivated Land
#### 4.2.1 Lost GPP Caused by the Occupation of Construction Land from 1990 to 2017
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multicolumn{2}{c}{**Fixed Effect Model**} & \multicolumn{2}{c}{**Random Effect Model**} \\ \cline{2-5}  & **Coefficient** & **T Value** & **Coefficient** & **T Value** \\ \hline \multicolumn{5}{c}{_Socio-Economic Factors_} \\ \(GDP\) & 0.0014 *** & 6.15 & 0.001 *** & 3.65 \\ \(PDI\) & 0.0003 * & 1.86 & \(-\)0.00009 & \(-\)0.69 \\ \(FAI\) & 0.0001 & 0.44 & 0.0002 & 0.76 \\ \(FI\) & \(-\)0.00006 *** & \(-\)4.06 & \(-\)0.00004 *** & \(-\)2.70 \\ \(TP\) & \(-\)0.011 & \(-\)1.41 & 0.017 *** & 5.39 \\ \(UR\) & \(-\)0.004 & \(-\)0.41 & \(-\)0.019 & \(-\)0.66 \\ \(UP\) & \(-\)0.006 & \(-\)0.81 & \(-\)0.012 ** & \(-\)2.30 \\ \multicolumn{5}{c}{_Policy Factors_} \\ \(NSM\) & \(-\)0.372 & \(-\)0.49 & 1.535 * & 1.65 \\ \(NBC\) & \(-\)3.247** & \(-\)2.14 & \(-\)0.423 & \(-\)0.33 \\ \(NT\) & 0.031 ** & 2.35 & 0.009 & 0.47 \\ \(ACL\) & 0.073 * & 1.78 & 0.004 *** & 2.63 \\ \(MRS\) & \(-\)6.558 & \(-\)0.57 & 21.425 ** & 1.97 \\ \(MH\) & 1.303 * & 1.93 & 1.586 * & 1.78 \\ \multicolumn{5}{c}{_Geographical Location Factors_} \\ _Eastern region_ & & & 18.223 ** & 2.41 \\ _Central region_ & & & 4.287 & 0.45 \\ _Plain area_ & & & 31.827 *** & 3.96 \\ _Year dummy_ & yes & & yes & \\ Constant & \(-\)179.81 & \(-\)1.06 & \(-\)25.429 *** & \(-\)3.17 \\ Sigma\_u & & 204.18 & & 11.90 \\ Number of & & 279 & & 279 \\ observations & & & & \\ \hline \hline \end{tabular} Note. *, **, and *** are significantly different from zero at the 10%, 5%, and 1% levels, respectively.  
\end{table} 
Table 2: Results of the estimations and tests of the models. As shown in Table 3, the maximum standardization coefficient of GDP was 0.635, indicating that GDP was the most important driving force for construction land expansion in the last ten years. Therefore, this paper predicted the expansion area of construction land in the future under the scenarios of low-, medium-, and high-speed economic growth according to the change in GDP. The base period was 2017, and other factors were kept at the average level from 2009 to 2017. According to the international economic growth standard, a GDP growth rate below 3% is considered low economic growth, a growth rate between 3% and 6% is considered medium-high growth, and a growth rate between 6% and 8% is considered high-speed growth. In this paper, 3% was the low-speed economic growth rate, and 6% was the medium-high-speed economic growth rate, and the prediction results of lost GPP caused by the expansion area of construction land and its occupation of cultivated land are shown in Table 4. If other factors remain unchanged, the scale of expansion of construction land in China will be 408.10 and 1017.28 hm\({}^{2}\) if the economic growth rate is estimated at 3% and 6% by 2030, and the reduction in cultivated land will be 330.56 and 824 hm\({}^{2}\), respectively. Correspondingly, the actual lost GPP of cultivated land were 2033.95 and 5070.05 t.